JP2017181025A - Near-field polarization microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a near-field polarization microscope which can accurately detect the magnetic domain of a sample while applying a magnetic field to the sample from the outside.SOLUTION: A near-field polarization microscope 1 includes: a cantilever 3 having a probe 2; a magnetic domain detecting optical system 4 for detecting the magnetic domain of a sample 8 by a near-field light generated by irradiating the probe 2 with a magnetic domain detecting laser light 11; an observation illumination optical system 5 for observing an irradiation state of the magnetic domain detecting laser light 11; an objective 6 common to the magnetic domain detecting optical system 4 and the observation illumination optical system 5; and magnetic field applying means 7 for applying a magnetic field to the sample 8 from the outside. Between an upper magnetic pole 43 and a lower magnetic pole 44 of the magnetic field applying means 7, the cantilever 3 made of a non-magnetic and non-conductive material and the sample 8 made of a magnetic material are arranged.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a near-field polarization microscope in which information on a sample is detected using near-field light generated when light enters a probe.

  Conventionally, a magnetic force microscope (MFM) has been used to detect a magnetic domain of a sample formed from a magnetic material. The cantilever of the magnetic force microscope has magnetism as described in the background art section of Patent Document 1 below. Since the cantilever has magnetism, a magnetic field generated from the surface of the sample can be measured.

JP2012-233845A

  However, in the magnetic force microscope, since the cantilever has magnetism, it is difficult to detect the magnetic domain of the sample while applying a magnetic field from the outside to the sample. This is because a magnetic cantilever is affected by a magnetic field applied from the outside, and an accurate magnetic domain of the sample cannot be detected.

  An object of the present invention is to provide a near-field polarization microscope that can accurately detect a magnetic domain of a sample while applying a magnetic field from the outside to the sample. It is also desirable to provide a near-field polarization microscope that can easily measure the magnetic hysteresis of a sample.

  The present invention has been made to solve the above problems, and the invention according to claim 1 is a near-field polarization microscope capable of detecting a magnetic domain of a sample having at least a surface having magnetism, and is non-magnetic. The probe has a concave probe formed of a material and tapering toward the tip. The probe is formed of a material that transmits light, and an inner surface is covered with a metal film. A cantilever arranged so that an atomic force acts between the sample and a magnetic domain detection optical system capable of detecting a magnetic domain of the sample by near-field light generated by irradiation of the probe inner surface with a magnetic domain detection laser beam; An observation illumination optical system capable of observing the irradiation state of the magnetic domain detection laser light by an optical image of the return light from the cantilever of illumination light having a wavelength band other than the wavelength of the magnetic domain detection laser light, the magnetic domain detection optical system, and An objective lens provided in common for the observation illumination optical system, and an upper magnetic pole and a lower magnetic pole disposed above and below the cantilever and the sample, and a magnetic field can be applied to the sample from the outside A near-field polarizing microscope comprising a magnetic field applying unit.

  The invention according to claim 2 is a scanning unit that scans the sample in a two-dimensional plane, a coordinate recording unit that moves the sample by a set amount by the scanning unit, and records a z coordinate at each point; Magnetic field changing means for changing an external magnetic field between set values, and storage means for storing information when the external magnetic field is changed at each point are further provided, based on the information from the magnetic domain detection optical system, The near-field polarization microscope according to claim 1, wherein magnetic hysteresis of a minute region of the sample can be measured.

  Furthermore, the invention according to claim 3 is the near-field polarization microscope according to claim 1 or 2, wherein an upper end portion of the lower magnetic pole is tapered toward the upper side.

  According to the first aspect of the present invention, when the magnetic field is applied to the sample by the magnetic field applying means in which the upper magnetic pole and the lower magnetic pole are arranged with the cantilever sandwiched between the cantilevers. The cantilever is not affected by the magnetic field by the magnetic field applying means. Therefore, the magnetic domain of the sample can be accurately detected while applying a magnetic field to the sample from the outside. Further, by using near-field light, the magnetic domain of the sample can be detected with a resolution exceeding the diffraction limit of light.

  According to invention of Claim 2, the magnetic hysteresis of a sample can be obtained with an AFM image.

  Furthermore, according to the third aspect of the present invention, the upper end portion of the lower magnetic pole is tapered, so that the magnetic field by the magnetic field applying means can be further strengthened.

It is a schematic block diagram which shows one Example of the near field polarizing microscope of this invention. It is the schematic which expands and shows a part of near field polarizing microscope of FIG. It is a schematic side view which shows the magnetic field application means of the modification of the near-field polarizing microscope of FIG. It is a schematic plan view of the magnetic field application means of FIG. It is a schematic block diagram which shows another modification of the near-field polarizing microscope of FIG.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

  1 and 2 are diagrams showing an embodiment of the near-field polarization microscope of the present invention. FIG. 1 is a schematic configuration diagram showing a part thereof in cross section, and FIG. 2 is an enlarged part of FIG. It is a schematic diagram and a part is further enlarged and shown. The near-field polarization microscope 1 of the present embodiment includes a cantilever 3 having a probe 2, a magnetic domain detection optical system 4, an observation illumination optical system 5, an objective lens common to the magnetic domain detection optical system 4 and the observation illumination optical system 5. 6 and magnetic field applying means 7. In this embodiment, the case where the magnetic domain of the sample 8 formed from a magnetic material is detected will be described. However, the sample 8 is not limited to this, and it is sufficient that at least the surface has magnetism.

  The cantilever 3 is made of a non-magnetic and non-conductive material that transmits light, and is made of silicon nitride in this embodiment. As shown in FIG. 2, the cantilever 3 has a one-end support type configuration and includes a plate-like beam portion 9 and a probe 2 provided at the other end portion of the beam portion 9. The cantilever 3 can be bent with one end side (the side opposite to the side where the probe 2 is formed) as a fulcrum.

  The probe 2 of the cantilever 3 has a concave shape that tapers toward the tip, and is formed in an inverted conical shape in this embodiment. The shape of the probe 2 is not limited to an inverted conical shape, and may be formed in an inverted pyramid shape, for example. A metal film 10 is formed on the inner surface of the probe 2 so that surface plasmon resonance occurs. In this embodiment, the film 10 is formed by metal vapor deposition using a metal such as gold, silver, or aluminum.

  The magnetic domain detection optical system 4 detects the magnetic domain of the sample 8. The magnetic domain detection optical system 4 includes a laser light source 12 for the magnetic domain detection laser light 11, a diaphragm 13 for the magnetic domain detection laser light 11 from the laser light source 12, a λ / 2 plate 14, a λ / 4 plate 15, and a dichroic mirror 16. With. As shown in FIG. 1, an aperture 13, a λ / 2 plate 14, a λ / 4 plate 15, and a dichroic mirror 16 are arranged in the order closer to the laser light source 12 along the optical path of the magnetic domain detection laser beam 11. In the present embodiment, the magnetic domain detection laser light 11 has a red wavelength of 633 nm, for example. The wavelength of the magnetic domain detection laser beam 11 is not limited to this, and may be a wavelength near the plasmon resonance wavelength of the cantilever.

  The magnetic domain detection optical system 4 includes a magnetic domain detection device 17 that detects the magnetic domain of the sample 8, a narrow band interference filter 18, a lens 19, a GT (Glan-Thompson) analyzer 20, and a λ / 4 plate. 21 and unnecessary reflection light exclusion means 22 for eliminating unnecessary reflection light to the magnetic domain detection device 17. The narrow band interference filter 18 is a filter that passes only light of a specific wavelength, and unnecessary light such as a surrounding fluorescent lamp is cut off, and only the laser light can pass. The magnetic domain detector 17 can detect the magnetic domain of the sample 8 based on the return light from the sample 8 due to the irradiation of the sample 8 with light. Further, the magnetic domain detection device 17 is, for example, a photodiode, a photomultiplier tube (photomultiplier), a spectroscope, or the like depending on the mode of return light from the sample 8 to be introduced and the target detection signal mode. Composed. When the narrow band interference filter 18 is used, the magnetic domain detector 17 is a photomultiplier tube. The unnecessary reflected light eliminating means 22 includes a pair of confocal lenses 23 and 23 that form a confocal point with the tip of the probe 2, and an aperture 24 disposed between the confocal lenses 23 and 23.

  The observation illumination optical system 5 observes the irradiation state of the magnetic domain detection laser beam 11 on the cantilever 3 and the positional relationship between the probe 2 and the sample 8. The observation illumination optical system 5 includes an illumination light source 25, a beam splitter 26, an imaging lens 27, and an observation device 28 that observes an optical image of the return light from the sample 8. The illumination light source 25 is, for example, a white light source that generates white illumination light 29. The beam splitter 26 is used for introducing illumination light 29 from the illumination light source 25 onto the optical axis or paraxial axis of the objective lens 6 described later. The observation device 28 includes a camera 30 and a monitor 31 on which an imaging optical image is projected. The objective lens 6 common to the observation illumination optical system 5 and the magnetic domain detection optical system 4 is a lens disposed closest to the sample 8.

  As described above, the magnetic domain detection laser beam 11 is a red laser beam. The illumination light source 25 has a wavelength band extending over a wavelength other than the wavelength of the magnetic domain detection laser beam 11, and a wavelength band extending over a wavelength other than the red wavelength in this embodiment. A white light source is used.

  The magnetic field applying means 7 applies a magnetic field to the sample 8 from the outside. As shown in FIG. 1, the magnetic field applying means 7 includes a base body 32 and a coil 33 provided on the base body 32. The base 32 includes a main body 34 and a lid 35 provided at the upper end of the main body 34. The main body 34 is a cylinder and is a cylinder arranged so as to form a cylindrical gap 37 between the iron core 36 and an iron core 36 formed from a truncated cone-shaped ferromagnetic material whose upper end portion tapers upward. And a disk-shaped connecting portion 39 to which the lower end portion of the iron core 36 and the lower end portion of the cylindrical portion 38 are connected. Here, each of the iron core 36 and the cylindrical portion 38 is fixed to the connecting portion 39 with screws.

  The lid body 35 is formed in a disc shape, and a notch 40 is formed in a part thereof. On the edge of the lower surface of the lid body 35, a mounting portion 41 is formed extending downward in a cylindrical shape. A circular introduction hole 42 is formed in the central portion of the lid 35 so as to penetrate the plate surface, and the introduction hole 42 and the cutout portion 40 communicate with each other. The coil 33 is disposed in the cylindrical gap 37. The mounting portion 41 of the lid body 35 is fixed to the upper surface of the cylindrical portion 38 of the main body 34 with screws. As a result, the lid 35 is the upper magnetic pole 43, while the iron core 36 of the base body 32 is the lower magnetic pole 44. A space is formed between the upper magnetic pole 43 and the lower magnetic pole 44 by the mounting portion 41 of the lid 35. A through hole 45 is formed in the mounting portion 41 of the lid 35 along the circumferential direction at a position facing the notch 40 of the lid 35 in the radial direction.

  The diameter and thickness of the introduction hole 42 are appropriately set according to the working distance and focal point of the objective lens 6 and other numerical aperture (NA). Further, the shape of the introduction hole 42 is not limited to a circular shape, and can be appropriately changed according to the working distance, the focal point, and the numerical aperture of the objective lens 6. Thereby, even if it is the structure of the magnetic field application means 7 of a present Example, a large numerical aperture and a short focus are realizable.

  The near-field polarizing microscope 1 according to the present embodiment includes a dichroic mirror 46, a probe stage 48 provided with a probe support piece 47, a sample stage 50 provided with a sample support piece 49, and a sample scanner. 51 is further provided.

  The dichroic mirror 46 can reflect and exclude the wavelength light of the magnetic domain detection laser light 11 from the white illumination light 29, which is red light of 633 nm in this embodiment. Further, the dichroic mirror 46 has a wavelength selectivity that allows light having a wavelength other than the wavelength of the magnetic domain detection laser light 11 to pass therethrough and directs the illumination light 29 together with the magnetic domain detection laser light 11 toward the objective lens 6. The sample stage 50 can be moved by the sample scanner 51 in the z-axis direction along the optical axis direction of the near-field polarization microscope 1 and in the x-axis and y-axis directions orthogonal to each other on a plane orthogonal to the z-axis direction.

  By the way, the cantilever 3 is arranged so that the tip of the probe 2 is close to the surface of the sample 8 so that an atomic force acts between the probe 2 and the sample 8. As shown in FIG. 2, the cantilever 3 is provided in the crystal resonator 52. The crystal resonator 52 is formed by cutting one of the two vibrating pieces 53, and the cantilever 3 is bonded to the remaining vibrating piece 53. The quartz oscillator 52 is provided on an excitation piezo 55 via a ceramic base 54, and this excitation piezo 55 is provided on the probe support piece 47 via a probe holder 56. The probe holder 56 and the probe support piece 47 are made of a nonmagnetic and nonconductive material, and are made of ceramic such as alumina in this embodiment. The probe support piece 47 is formed in an elongated plate shape, and a probe holder 56 is provided at the tip. The tip of the probe support piece 47 is inserted into the base 32 through the notch 40 of the lid 35. At this time, the cantilever 3 is arranged between the upper magnetic pole 43 and the lower magnetic pole 44, and the probe 2 is arranged corresponding to the introduction hole 42 of the lid 35.

  On the other hand, the sample 8 is provided on the sample support piece 49 via the sample holder 57. The sample holder 57 and the sample support piece 49 are made of a nonmagnetic and nonconductive material, and are made of ceramic such as alumina in this embodiment. The sample support piece 49 is formed in an elongated plate shape, and a sample holder 57 is provided at the tip. The sample support piece 49 is inserted into the base body 32 through a through hole 45 formed in the lid body 35. At this time, the sample 8 is disposed below the cantilever 3 between the upper magnetic pole 43 and the lower magnetic pole 44 and corresponding to the introduction hole 42 of the lid 35.

  Next, an operation for detecting the magnetic domain of the sample 8 using the near-field polarization microscope 1 of the present embodiment will be described. Here, the near-field light will be described. By focusing the far-field light of the magnetic domain detection laser light 11 irradiated from the laser light source 12 on the tip of the probe 2, plasmon resonance is excited at the boundary surface between the probe 2 and the film 10, and this is applied to the probe 2. Propagating to the tip side, near-field light (near field light) is generated from the tip, and the sample 8 is irradiated with the near-field light. The spot diameter due to the near-field light is not restricted by the diffraction limit, and does not depend on the numerical aperture of the objective lens 6 and the wavelength of the magnetic domain detection laser light 11, so that it can be a very small irradiation spot diameter.

  A magnetic field is applied to the sample 8 from the outside by the magnetic field applying means 7. Specifically, by applying a current to the coil 33, the lid 35 and the iron core 36 become magnetic poles 43 and 44, respectively, and a magnetic field can be generated. Thereby, in a present Example, a strong magnetic field, for example, a 1 Tesla magnetic field, can be generated. In this way, the magnetic domain of the sample 8 can be detected while applying a magnetic field from the outside.

  In the near-field polarizing microscope 1, the illumination light 29 is reflected by the beam splitter 26, passes through the dichroic mirror 46, is collected by the objective lens 6, and is passed through the introduction hole 42 of the lid 35 and the cantilever 3 and the sample. 8 is irradiated. The return light of the illumination light 29 applied to the cantilever 3 and the sample 8 passes through the lens 27 and is observed by the observation device 28. Based on the observation result, the reference position of the sample 8 is adjusted by the sample scanner 51. The sample scanner 51 can move the sample stage 50 in the xy direction (horizontal direction) and the z direction (vertical direction). Note that the setting position of the cantilever 3 is adjusted as necessary.

  Thereafter, the sample stage 50 is moved in the x and y directions by the sample scanner 51, and the spot of the near-field light from the tip of the probe 2 by the magnetic domain detection laser beam 11 is scanned on the surface of the sample 8. In this way, the sample 8 is moved while the cantilever 3 is fixed. The magnetic domain detection laser beam 11 passes through the λ / 2 plate 14 through the diaphragm 13 and then passes through the λ / 4 plate 15. At this time, the magnetic domain detection laser beam 11 is converted into linearly polarized light by the λ / 2 plate 14 and is converted into circularly polarized light or elliptically polarized light by the λ / 4 plate 15. The circularly polarized far-field light passes through the dichroic mirror 16, is reflected by the mirror 58 and the mirror 59, is reflected by the dichroic mirror 46, is collected by the objective lens 6, and is introduced into the introduction hole 42 of the lid 35. The near-field light is obtained from the tip, and the sample 8 is irradiated with the near-field light.

  When focusing on the tip of the probe 2, normal light propagating in the air is reflected without being transmitted at an inner diameter less than half the wavelength of the magnetic domain detection laser beam 11. Only near-field light is propagated to the tip side from this portion. Plasmon resonance is excited at the interface between the probe 2 and the film 10, and this is propagated toward the tip of the probe 2, and near-field light oozes out from the tip of the probe 2. At this time, since the tip of the probe 2 is close to the surface of the sample 8, the near-field light of this minute spot is irradiated onto the surface of the sample 8.

  The near-field light irradiated on the sample 8 is reflected by the surface of the sample 8 and passes through the objective lens 6 as return light, reflected by the dichroic mirror 46, then reflected by the mirror 59 and the mirror 58, and further Reflected by the dichroic mirror 16. Then, the magnetic domain of the sample 8 is detected by the magnetic domain detection device 17 provided in the magnetic domain detection optical system 4.

  In order to detect a magnetic domain from the surface of the sample 8, it is necessary to detect the magnetic Kerr effect. When the near-field light is reflected by the sample 8, the polarization plane is rotated according to the magnetization direction of the sample 8. Such return light travels from the objective lens 6 to the dichroic mirror 16 as described above, and further travels to the λ / 4 plate 21 via the unnecessary reflected light exclusion means 22. At this time, the return light of the unnecessary far-field light reflected by the inner surface of the probe 2 also travels from the objective lens 6 to the dichroic mirror 16 in the same manner as the return light of the near-field light, and further passes the unnecessary reflected light exclusion means 22. Then, the process proceeds to the λ / 4 plate 21.

  The return light from the sample 8 and the return light of unnecessary far-field light reflected by the inner surface of the probe 2 have different optical path lengths to the λ / 4 plate 21. As a result, both return lights converted into linearly polarized light by the λ / 4 plate 21 are introduced into the GT analyzer 20 in a state where the angles of the polarization planes are different. Here, only the return light from the sample 8 can be taken out by adjusting the polarization angle of the GT analyzer 20. That is, the return light of unnecessary far field light reflected by the inner surface of the probe 2 can be eliminated. In this way, only the light that has been subjected to magnetic domain detection is introduced into the magnetic domain detection device 17 via the lens 19 and the narrowband interference filter 18, and the output converted into an electrical signal can be taken out.

  In the unnecessary reflected light eliminating means 22, diffracted light that is not in the confocal relationship by the pair of confocal lenses 23, 23 can be cut off by being cut off by the aperture 24 arranged at the confocal position. For example, when the signal from the probe 2 is detected by the unnecessary reflected light eliminating means 22, the diameter of the pinhole of the aperture 24 and the magnification of the confocal lens 23 and the objective lens 6 can be detected so that only the signal can be detected. It is set by the difference with the magnification.

  By the way, the cantilever 3 is controlled so that the distance between the probe 2 and the sample 8 is constant. As shown in FIGS. 1 and 2, the crystal resonator 52 provided with the cantilever 3 is provided with an excitation electrode and a detection electrode (not shown). When an alternating voltage is applied to the excitation electrode, the vibrating piece 53 of the crystal resonator 52 is flexibly vibrated, thereby causing the probe 2 of the cantilever 3 to vibrate in a direction substantially perpendicular to the surface of the sample 8. be able to.

  The sample scanner 51 includes fine movement means that can adjust the distance between the probe 2 and the sample 8, and scanning means that relatively scans the probe 2 and the sample 8 in a two-dimensional plane. . The sample scanner 51 and the sample stage 50 are connected, so that the sample stage 50 and eventually the sample 8 can be moved by the sample scanner 51 in the xy direction (horizontal direction) and the z direction (vertical direction). .

  The tip of the probe 2 and the surface of the sample 8 are brought close to each other in a state where an alternating voltage is applied to the crystal unit 52 and the resonator element 53 is resonated. As a result, an atomic force acts between the tip of the probe 2 and the surface of the sample 8, and the vibration state such as the frequency and amplitude of the vibrating piece 53 changes, and the piezoelectric current generated by the vibration of the quartz crystal resonator 52. Is changed.

  A PLL (Phase Locked Loop) circuit 61 is connected to the detection electrode of the crystal resonator 52 via a preamplifier 60. In the preamplifier 60, the piezoelectric current generated by the vibration of the crystal resonator 52 is detected and amplified and changed into an electric signal, which is output to the PLL circuit 61. In the PLL circuit 61, the amount of change in the resonance frequency of the resonator element 53 is detected, an electric signal representing the amount of change is generated, and the generated electric signal is output to the control unit 62. The control unit 62 outputs a control signal to the sample scanner 51 so that the above-described frequency change amount is kept constant. Then, the sample 8 is moved relative to the probe 2 in a two-dimensional plane while adjusting the distance between the probe 2 and the sample 8 to be constant by the sample scanner 51.

  In the near-field polarizing microscope 1 of the present embodiment, it is preferable that the magnetic hysteresis in the minute region of the sample 8 can be measured together with the AFM image. In this case, the near-field polarizing microscope 1 of this embodiment moves the sample 8 by a set amount by the scanning unit of the sample scanner 51 and records the z coordinate at each point, and an external magnetic field between the set values. And a storage means for storing information when the external magnetic field is changed at each of the points. When moving the scanning means of the sample scanner 51 by a set amount, a terminal device constituted by a personal computer and the sample scanner 51 are connected, and the set amount may be set in the terminal device.

  The coordinate recording means is means for recording the z coordinate at each point of the sample 8. The coordinate recording means is connected to the sample scanner 51 and can record the information of the z coordinate sent from the sample scanner 51. Here, the z coordinate is the height information of the undulation of the sample 8. The z coordinate is recorded in the coordinate recording means in association with the xy coordinate (location on the sample surface) of the sample 8. The magnetic field changing means is provided in the magnetic field applying means 7 and connected to the terminal device. In this terminal device, the value of the magnetic field to be changed is set. In this embodiment, for example, it is set so as to continuously vary from +1 Tesla to -1 Tesla and from -1 Tesla to +1 Tesla. The storage means is connected to the magnetic domain detection device 17, and can store information when the magnetic field is changed by the external magnetic field changing means at each point. That is, the stored information is associated with the z coordinate at each point. Thereby, the magnetic hysteresis for each point can be obtained.

  Therefore, an AFM image can be obtained by two-dimensionally displaying the acquired z coordinate information. In addition, two pieces of three-dimensional magnetic hysteresis data can be obtained in which the magnetic axis is taken as the z axis and the surface location of the sample is taken as the xy axis. Here, the two are a case where the magnetic field is changed from -1 Tesla to +1 Tesla and a case where the magnetic field is changed from +1 Tesla to -1 Tesla.

  After data acquisition, by slicing along a specific magnetic axis, for example, a magnetic image (two-dimensional) at 0.5 Tesla when increased from zero magnetic field can be obtained together with an AFM image. Further, when confirming the magnetic hysteresis at a specific location, the magnetic hysteresis curve at that location may be extracted.

  According to the near-field polarization microscope 1 of the present embodiment, the cantilever 3 disposed between the upper magnetic pole 43 and the lower magnetic pole 44 is formed of a nonmagnetic material. It is not affected by the applied magnetic field. Therefore, the magnetic domain of the sample 8 can be accurately detected while applying a magnetic field from the outside. In addition to this, according to the near-field polarization microscope 1 of the present embodiment, the sample support piece 49, the sample holder 57, the probe holder 56, and the probe support piece arranged between the upper magnetic pole 43 and the lower magnetic pole 44. Since 47 is formed of a nonmagnetic material, they are not affected by the magnetic field.

  Further, according to the near-field polarization microscope 1 of the present embodiment, the cantilever 3, the sample support piece 49, the sample holder 57, the probe holder 56, and the probe support piece 47 are formed of a nonconductive material, so that the vortex The influence of current can be suppressed. Further, according to the near-field polarization microscope 1 of the present embodiment, the sample support piece 49 and the probe support piece 47 are inserted from the outer peripheral surface of the base 32 between the upper magnetic pole 43 and the lower magnetic pole 44. The distance between the upper magnetic pole 43 and the lower magnetic pole 44 can be reduced. Further, according to the near-field polarizing microscope 1 of the present embodiment, the magnetic domain of the sample 8 can be detected using the near-field light while applying a magnetic field, so that the change in the magnetization of the magnetic dot in the minute region can be observed. Can do. Furthermore, according to the near-field polarization microscope 1 of the present embodiment, the upper end portion of the lower magnetic pole 44 is formed to be tapered, so that the magnetic field can be made stronger.

  The near-field polarizing microscope of the present invention is not limited to the configuration of the above-described embodiment, and can be changed as appropriate. For example, the magnetic field applying unit 7 is not limited to the configuration of the above embodiment. 3 and 4 are views showing a modification of the near-field polarization microscope of FIG. 1, FIG. 3 is a schematic side view of the magnetic field applying means, and FIG. 4 is a schematic plan view of the magnetic field applying means. And a sample are arranged.

  The magnetic field applying means 7 of this modification is provided on the iron core 72, an upper return yoke 70 and a lower return yoke 71 that are spaced apart from each other, an iron core 72 that connects the upper return yoke 70 and the lower return yoke 71, and And a column body 74 provided on the lower return yoke 71. One end of the upper return yoke 70 and the lower return yoke 71 are connected by a cylindrical iron core 72, and a coil 73 is provided on the iron core 72. The column 74 is formed in a columnar shape and is erected on the other end of the lower return yoke 71. At this time, the other end of the upper return yoke 70 and the upper end of the column 74 are disposed so as to correspond to each other with a gap left therebetween. The upper end of the column 74 is formed in a truncated cone shape that tapers as it goes upward. Thus, the upper return yoke 70 is the upper magnetic pole 43, and the column body 74 is the lower magnetic pole 44.

  The cantilever 3 and the sample 8 are disposed in a gap between the upper return yoke 70 that becomes the upper magnetic pole 43 and the column 74 that becomes the lower magnetic pole 44. In this state, when an electric current is passed through the coil 73, the upper return yoke 70 and the column 74 become the upper magnetic pole 43 and the lower magnetic pole 44, respectively, and a magnetic field can be generated and the magnetic field can be applied to the sample 8. it can. In this modification, the elongated plate-like probe support piece 47 and the sample support piece 49 are not required, but the other cantilevers 3, the holders 56 and 57, etc. are made of a nonmagnetic material, so that the influence of the magnetic field is reduced. I do not receive it. In addition, the influence of eddy currents can be suppressed by forming them from a non-conductive material. Moreover, in the magnetic field application means 7 of this modification, the whole near-field polarizing microscope 1 can be made compact. Furthermore, the near-field polarizing microscope 1 using the magnetic field applying means 7 of this modification can easily apply the configuration of an existing atomic force microscope.

  In the above-described embodiment, the cantilever 3 is vibrated by the crystal resonator 52, but the cantilever 3 may be vibrated by the excitation piezo 55. FIG. 5 is a schematic configuration diagram showing another modified example of the near-field polarization microscope of FIG. 1, and a part thereof is omitted. The near-field polarizing microscope 1 of this modification example has basically the same configuration as that of the above embodiment. Therefore, in the following description, differences between the two will be mainly described, and corresponding portions will be described with the same reference numerals.

  As shown in FIG. 5, the cantilever 3 is directly provided on the excitation piezo 55. The excitation piezo 55 is excited by the excitation frequency of the resonance frequency of the cantilever 3 from an output device (not shown). Accordingly, the vibration of the excitation piezo 55 is transmitted to the cantilever 3 and the cantilever 3 is vibrated. The near-field polarization microscope 1 of this modification further includes a displacement detection optical system 63 that detects the displacement of the cantilever 3 and a dichroic mirror 64. The displacement detection optical system 63 includes a displacement laser light source 66 for the displacement detection laser light 65, a displacement detection device 67 for detecting the displacement of the cantilever 3 by the light, and a lens 68. In this modification, the film 10 is continuously formed on the surface of the beam portion 9 from the inner surface of the probe 2 except for one end portion of the beam portion 9.

  The displacement detector 67 is a four-division photodiode in this modification, and can detect the displacement of the cantilever 3 by the return light of the displacement detection laser beam 65 from the cantilever 3. In this embodiment, the displacement detection laser beam 65 has a green wavelength of 532 nm, for example. The objective lens 6 is common to the displacement detection optical system 63, the observation illumination optical system 5, and the magnetic domain detection optical system 4. Thereby, simplification of a structure, size reduction of an occupation space, and the improvement of an assembly precision can be aimed at. The dichroic mirror 64 can reflect and exclude the wavelength light of the displacement detection laser light 65 from the illumination light 29, in this embodiment, green light of 532 nm. Further, the dichroic mirror 64 has wavelength selectivity that allows light having a wavelength other than the wavelength of the displacement detection laser light 65 to pass therethrough and directs the illumination light 29 together with the displacement detection laser light 65 toward the objective lens 6.

  In the near-field polarizing microscope 1 of this modification, the magnetic domain of the sample 8 is detected in the same manner as the near-field polarizing microscope 1 of the above embodiment. At this time, the displacement detection laser light 65 from the displacement laser light source 66 is reflected by the dichroic mirror 64, passes through the dichroic mirror 46, passes through the objective lens 6, and is reflected by the film 10 of the cantilever 3. This return light is introduced into the displacement detection device 67 via the lens 68. Since the return light changes in the incident angle to the displacement detection device 67 (that is, change in spot shape) or the position according to the bending of the cantilever 3, that is, the displacement, each part of photoelectric conversion in the displacement detection device 67 Changes in the amount of incident light. Therefore, by calculating the output from these, it is possible to detect the deflection of the cantilever 3 and thus the atomic force. That is, the interval between the probe 2 and the sample 8 can be detected.

  A signal that detects the interval between the probe 2 and the sample 8 is input to the control device 69, and a control signal is output from the control device 69 to the sample scanner 51. Then, the sample scanner 51 adjusts the sample stage 50 in the z-axis direction. Thereby, the space | interval of the probe 2 and the sample 8 can always be kept constant. In other words, the near-field light is always applied to the surface of the sample 8 under a certain condition.

  In the above embodiment, the crystal resonator 52 is directly vibrated, but may be vibrated by the excitation piezo 55. In this case, by vibrating the excitation piezo 55, the crystal resonator 52 is vibrated, and as a result, the cantilever 3 is vibrated. In the above-described embodiment, the λ / 4 plate 15 is provided in the magnetic domain detection optical system 4, but this may not be used. In this case, the magnetic domain detection laser light 11 is linearly polarized by the λ / 2 plate 14 and proceeds to the dichroic mirror 16. In addition, the λ / 4 plate 15 and the λ / 4 plate 21 may not be used.

  In the above-described embodiment, the probe support piece 47 and the sample support piece 49 are arranged so as to face each other in the radial direction of the base 32. However, the present invention is not limited to this, and the probe support piece 47 and You may arrange | position so that the sample support piece 49 may mutually orthogonally cross. Moreover, in the said Example, although the magnetic domain detection apparatus 17 was used as the photomultiplier tube, it is good also as a spectrometer. In this case, the narrowband interference filter 18 is not used, and the dichroic mirror 16 and the dichroic mirror 46 are beam splitters that are half mirrors. Further, a beam splitter is disposed between the unnecessary reflected light eliminating means 22 and the λ / 4 plate 21 or between the GT analyzer 20 and the lens 19, and the return light is transmitted to the photomultiplier tube. You may branch to the light reflected by a splitter. In this case, the light reflected by the beam splitter is introduced into the spectrometer, and the detection signal from the photomultiplier tube and the detection signal from the spectrometer can be acquired simultaneously.

  In the above-described embodiment, the frequency of the resonator element 53 of the crystal resonator 52 is detected by the PLL circuit 61. Based on this, the distance between the probe 2 and the sample 8 is kept constant. For example, the above-described displacement detection optical system 63 may be used. Further, in the modification, the vibration of the cantilever 3 due to the vibration of the excitation piezo 55 is detected by the displacement detection optical system 63. However, the present invention is not limited to this. For example, the frequency of the excitation piezo 55 is the PLL circuit 61. It is good also as a structure detected by. The PLL circuit 61 is configured to contact the surface of the sample 8 while touching the surface of the sample 8 with the cantilever 3 while detecting the irregularities on the surface of the sample 8 by the movement of the cantilever 3, or by forcibly exciting the cantilever 3 at the resonance frequency. It also supports a tapping method.

DESCRIPTION OF SYMBOLS 1 Near field polarizing microscope 2 Probe 3 Cantilever 4 Magnetic domain detection optical system 5 Observation illumination optical system 6 Objective lens 7 Magnetic field application means 8 Sample 10 Film 11 Magnetic domain detection laser beam 17 Magnetic domain detection device 28 Observation device 29 Illumination light 43 Upper magnetic pole 44 Bottom pole

Claims (3)

A near-field polarization microscope capable of detecting a magnetic domain of a sample having at least a surface having magnetism,
The probe is formed of a non-magnetic material and has a concave probe that tapers toward the tip. The probe is formed of a material that transmits light and has an inner surface covered with a metal film. A cantilever arranged such that an atomic force acts between the needle and the sample;
A magnetic domain detection optical system capable of detecting a magnetic domain of the sample by near-field light by irradiation of the probe inner surface with a magnetic domain detection laser beam;
An observation illumination optical system capable of observing the irradiation state of the magnetic domain detection laser light by an optical image of the return light from the cantilever of the illumination light having a wavelength band other than the wavelength of the magnetic domain detection laser light;
An objective lens provided in common for the magnetic domain detection optical system and the observation illumination optical system;
A near-field polarization microscope comprising: an upper magnetic pole and a lower magnetic pole arranged above and below the cantilever and the sample, and a magnetic field applying unit capable of applying a magnetic field from the outside to the sample. Scanning means for scanning the sample in a two-dimensional plane;
A coordinate recording means for moving the sample by a set amount by the scanning means and recording the z coordinate at each point;
Magnetic field changing means for changing the external magnetic field between set values;
Storage means for storing information when the external magnetic field is changed at each of the points;
The near-field polarization microscope according to claim 1, wherein magnetic hysteresis of a minute region of the sample can be measured based on the information from the magnetic domain detection optical system. The near-field polarization microscope according to claim 1, wherein an upper end portion of the lower magnetic pole is formed to taper as it goes upward.

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