JPH11126449A - Functional element composed of composite layer of magnetostrictive and piezoelectric materials, and magnetic head equipped with the element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a minute displacement or minute contact pressure to be controlled without being affected by hysteresis or the change with time by laminating a piezoelectric material and a magnetostriction material, detecting a change in the former material with the latter, and feeding back to the control voltage of the piezoelectric material. SOLUTION: A PZT based piezoelectric ceramic 3, which is a piezoelectric body with an electrode 2 formed on both faces and polarized, is stuck to one face of an elastic substrate 1 composed of glass to form an actuator. On the top of it, an amolphous film 5, a magnetostriction film, is sputtered through an insulation film 4 of SiO2 to form a deformation sensor. With a voltage applied to the electrode 2 of the actuator, varying the applied voltage in positive and negative directions, the ceramic plate 3 bends vertically. Since the amolphous film 5 changes in magnetic permeability in accordance with the deflection of the elastic substrate 1, its deflection quantity is known by impressing a high frequency carrier at both ends of a Mianda pattern and detecting inductance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention includes an actuator used for a mechanism that requires precise positioning and a constant contact pressure in fields such as optical communication, magneto-optical recording, and magnetic recording. The present invention relates to a functional element and a magnetic head including the functional element.

[0002]

2. Description of the Related Art Conventionally, electromagnetic actuators have been applied to a wide range of fields due to the convenience of electrical control. Electromagnetic actuators use electromagnetic force as the source of the driving force, and basically require a current to flow through the coil, whereas piezoelectric types use the inverse piezoelectric effect of the piezoelectric material as the source of the driving force. , Voltage driving, a configuration with low power consumption is basically possible. On the other hand, the field of application where the amount of displacement is small is limited, but within the range of the amount of displacement below a certain level, advantages such as small size, light weight, power saving and high-speed response are basically provided as compared with the electromagnetic type. In recent years, with the miniaturization and power saving of devices and the emergence of a new type of recording method, this piezoelectric actuator has been regarded as promising.

[0003] Piezoelectric actuators are mechanically divided into the following four types.
Can be divided into species. a Short plate type b Bimorph type (or monomorph type) c Laminated type d Ultrasonic motor type To briefly explain this type, a is a simple configuration in which an electrode is formed on a piezoelectric material. It can be divided into a horizontal effect type that uses a displacement and a vertical effect type that uses a displacement in a direction parallel to the direction. This method has a simple structure and is robust, but has a small amount of displacement and has very few uses. b is a structure in which two rectangular single-plate types are bonded together. One end is fixed and the other end is free. When an electric field is applied so as to cause expansion deformation on one side and shrinkage deformation on the other side, a free state is obtained. This is based on the fact that the end is largely bent and deformed, and is provided with a displacement enlarging mechanism in the configuration, and has a relatively wide range of applications. When one side is made of a normal elastic body, the driving force is reduced by half, but a relatively large displacement can be obtained at the free end. Therefore, this method is also widely used and is called a monomorph. However, there is a disadvantage common to both of them, which is that the generated force is weaker as the displacement is larger. In the following description, it is assumed that the bimorph type includes the monomorph type.

[0004] The lamination type c has a structure in which a plurality of veneers are laminated in the thickness direction, and an electric field is applied to each veneer so that displacement in the same direction occurs in the thickness direction of the longitudinal effect. In such a configuration, the displacement is synthesized by the number of stacked layers, so that the displacement is enlarged by the number of stacked layers, and the generated force is large. The ultrasonic motor method d obtains rotation or linear motion by combining standing waves and traveling waves generated by the ultrasonic transducer. The vibrator may be of a magnetostrictive type, and need not necessarily be of a piezoelectric type. In the following description, the piezoelectric actuator means the above a, b, and c. The present invention relates to a b-bimorph (or monomorph) actuator among the piezoelectric actuators described above, a functional element using the same, and a magnetic head including the functional element.

[0005]

As described in the previous section,
Bimorph-type actuators are used in a wide range of fields because they can obtain relatively large displacements with a simple configuration.However, a common problem with piezoelectric actuators is that displacement hysteresis and time-dependent changes are large. This problem is remarkable in the bimorph type. More specifically, when the voltage is first gradually increased from 0 to be displaced to a certain amount, and then gradually decreased to 0, the displacement amount is the same for the same voltage at the time of pressure increase and pressure decrease. Is different. Therefore, the displacement does not completely return. Also, if the apparatus is left with a constant voltage applied, the displacement gradually changes. It is said that the main cause of the change with time is that the constituent piezoelectric material, the intermediate elastic material, or the bulk material is used, and the adhesive layer between them causes creep deformation during long-term deformation. In particular, the presence of the adhesive layer has an adverse effect on aging.

As a countermeasure against the hysteresis, an improvement has been made by controlling the electric charge on the electrode instead of controlling the applied voltage, but the accuracy is not always sufficient. Invalid.
In this regard, if it is possible to always detect the displacement and feed it back to the drive voltage, the problem of hysteresis and the problem of aging can be solved. However, when the conventional displacement detection method is an optical type or a capacitance conversion type, there is a disadvantage that the structure becomes large.

The problem to be solved by the present invention is to provide a functional element which detects displacement with a simple structure, feeds it back to a driving power source, and can always specify a required displacement. Also, like the functional element of the present invention,
If one element can realize the function of detecting this displacement at the same time as the occurrence of the displacement, an object comes in contact with this element from the outside and the displacement generated when it is displaced by external force is detected, and it is fed back to the drive voltage This makes it possible to provide an element having a function of self-controlling the contact pressure with the object within a certain range.

In recent years, magnetic heads used in hard disk drives (HDDs), which have rapidly become smaller and have higher recording densities, are required to have higher precision as recording densities increase. For reading and writing, a contact type has been adopted in addition to the conventional floating type. When a contact magnetic head is employed in the hard disk drive system, the recording density can be significantly increased. In the levitation method, the recording density is lower because the distance from the magnetic disk is 40 to 50 nanometers. On the other hand, in the contact type, the distance between the element and the disk surface is controlled to 10 nanometers or less, and the recording density can be dramatically improved.

However, there is a problem with this. In the contact type, the smoothing agent of the magnetic disk begins to melt due to friction, and the recording / reproducing element is shaved, and the shavings are generated, thereby reducing the durability of the magnetic head and the disk. There was a problem of lowering. In this case, for both the floating type and the contact type, the positional relationship between the recording track of the magnetic disk and the head, that is, the interval and position between the magnetic head and the magnetic disk in the floating type, and the contact pressure and position in the contact type How to maintain such constant and high precision is an important issue for stable operation. The present invention is particularly effective for the task of finely controlling the horizontal, vertical and contact pressure of the magnetic head used in the HDD.

[0010]

According to the present invention, there are provided: (1) a piezoelectric material functioning as an actuator element and a magnetostrictive material having a sensor function are laminated, and a displacement due to distortion or deformation of the piezoelectric material is detected by the magnetostrictive material to obtain electric power; A functional element composed of a composite layer of a magnetostrictive material and a piezoelectric material characterized in that the signal is converted into a signal and this is fed back to a control voltage of the piezoelectric material to correct the displacement of the laminated body. One or more of a piezoelectric material functioning as an actuator element and a magnetostrictive material having a displacement sensor function are formed in a part of a drive mechanism of a contact type magnetic head functioning as follows. Strain or deformation is detected by a magnetostrictive material and converted into an electric signal, which is fed back to an actuator made of a piezoelectric material and compressed. By correcting the displacement of the electric material, the magnetic head is brought into contact with the magnetic disk with a constant contact pressure, and / or the position of the magnetic head is moved relative to the magnetic disk by the displacement due to the distortion or deformation of the piezoelectric material. At the same time as fine control in the horizontal direction, the deviation of the displacement from the reference is detected by a magnetostrictive material and converted into an electric signal, which is fed back to the actuator of the piezoelectric material to correct the displacement of the piezoelectric material. A magnetic head provided with a functional element comprising a composite layer of a magnetostrictive material and a piezoelectric material, characterized in that the positional relationship between a magnetic head portion and a track on a magnetic disk surface is finely adjusted. A piezoelectric material that functions as an actuator element and a displacement sensor function are added to a part of the drive mechanism of the floating magnetic head that functions. One or more magnetostrictive materials are formed, and the position of the magnetic head is finely controlled in the vertical and / or horizontal directions with respect to the magnetic disk by the displacement due to the distortion or deformation of the piezoelectric material, and at the same time, the amount of the displacement from the reference The displacement is detected by a magnetostrictive material and converted into an electric signal, which is fed back to an actuator made of a piezoelectric material to correct the displacement of the piezoelectric material, thereby displacing the magnetic head with the recording medium and / or within the magnetic disk. A magnetic head provided with a functional element comprising a composite layer of a magnetostrictive material and a piezoelectric material, characterized in that the positional relationship with the track is finely adjusted. 4. The piezoelectric material and / or the magnetostrictive material is a bulk material. The functional element according to any one of the above 1 to 3 or the magnetic head provided with the functional element. 5 The piezoelectric material and / or the magnetostrictive material is a thin film. 6. The functional element according to any one of 1 to 3 above, or a magnetic head provided with the functional element. 6. The magnetostrictive material is an amorphous Fe-Co-Si-B alloy. Or a magnetic head provided with the functional element. 7. The method according to 1 above, wherein a displacement due to strain or deformation of the piezoelectric material is detected by a magnetostrictive material using a high-frequency carrier of 1 MHz to 2 GHz. And a magnetic head provided with the functional element.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, a piezoelectric material functioning as an actuator element and a magnetostrictive material having a sensor function are laminated, and a displacement due to distortion or deformation of the piezoelectric material is detected by the magnetostrictive material and converted into an electric signal. Then, this is fed back to the control voltage of the piezoelectric material to correct the displacement of the laminated body. Hereinafter, a case where a bulk material is used as the piezoelectric material will be specifically described. In addition,
A thin film can be used as the piezoelectric material. When a thin film is used, the adhesive required for the bulk material is not required, so that there is an advantage that there is no change over time peculiar to the adhesive, and the accuracy of positioning and the like is further improved. As described above, although the thin film has a difference in such forming means and characteristics from the bulk material, it is structurally the same. Means for forming a thin film include a sol-gel method, a sputtering method, and a CVD method.

A piezoelectric plate having electrodes formed on both sides on an elastic substrate is bonded to both sides. Next, a film of a magnetostrictive material is formed on this upper surface via an insulating layer (film). In this case, the piezoelectric plate may be on one side of the elastic substrate, or a film of magnetostrictive material may be formed on the surface of the elastic substrate on the opposite side of the piezoelectric plate. Electrodes are formed at both ends of the thus formed magnetostrictive thin film, and the deflection of the substrate can be read as a change in impedance from a change in inductance between terminals. In this case, by making the shape of the magnetostrictive thin film a meander pattern, it can be grasped as a larger change. When a soft magnetic film, which is an iron-based amorphous film, is used as the magnetostrictive thin film, a larger magneto-mechanical coupling coefficient can be obtained. As a result, the magnetic characteristic changes sensitively and significantly even with a small strain, and an element having a sensor function highly sensitive to bending can be obtained. Displacement due to distortion or deformation of the piezoelectric material is 1 MHz due to the magnetostrictive material.
Detect using a high frequency carrier of ~ 2 GHz. 5 μm for relatively low frequency within the above frequency range
It can be used for a thick film having a thickness of about 1 μm, and is suitable for a thin film having a thickness of about 1 μm for higher frequencies. The selection of this frequency can be appropriately selected depending on the thickness of the magnetic film. In addition, 1MHz
If the frequency is lower than this, mechanical resonance occurs and the function as a sensor is impaired, which is not preferable. In the case of a frequency exceeding 2 GHz, a leaked radio wave appears,
The magnetic film spontaneously resonates and the characteristics deteriorate. Further, it is not preferable because recording / reproducing becomes substantially difficult. From the above, 1M
It is appropriate to use a high-frequency carrier between 2 Hz and 2 GHz.

When the piezoelectric body is formed of piezoelectric ceramics,
A contraction stress is generated in the piezoelectric body with respect to the electric field in the polarized direction, so that the entire substrate can be bent. Also,
In response to an electric field in the opposite direction, the piezoelectric body generates an elongational stress, causing the entire substrate to bend and deform in the opposite direction. Such bending of the piezoelectric material similarly occurs in a thin film material formed by a sol-gel method, a sputtering method, a CVD method, or the like. Next, the principle of detecting distortion or deformation generated by a piezoelectric actuator in a composite element of a piezoelectric body and a magnetostrictive thin film and a change in impedance as a sensor element will be described.

As an example, electrodes are formed on the upper and lower surfaces of a piezoelectric ceramic plate, and a voltage is applied in the thickness direction. In this case, the longitudinal stress σp generated from the piezoelectric body is given by Equation 1.

[0015]

(Equation 1) Here, d31 is the piezoelectric constant of the piezoelectric body, V is the applied voltage, t
Is the thickness of the piezoelectric body, and Ep is the Young's modulus of the piezoelectric body. The stress σp causes the entire element to bend, and the soft magnetic film, that is, the magnetostrictive film is distorted. Assuming that this distortion amount is ΔL / L, Ma
rcus model (M. Marcus, Ferroelectrics, 57 (1980), 20
From 3), the magnetic permeability μ of the soft magnetic film is given by the following equation (2).

[0016]

(Equation 2) Here, Ms is the saturation magnetization of the soft magnetic film, Kμ is the uniaxial magnetic anisotropy constant, λs is the saturation magnetostriction constant, and Ef is the Young's modulus. From equation (2), the soft magnetic film is distorted (ΔL / L) due to the stress σp generated in the piezoelectric body, thereby changing the effective magnetic anisotropy of the soft magnetic film and consequently the magnetic permeability μ. Will be. From equation (2), a change in the magnetic permeability depends not only on the saturation magnetostriction constant of the soft magnetic film but also on the magnitude of the Young's modulus, and therefore a material having a large mechanical coupling coefficient determined by the two is required.

Table 1 shows a list of magneto-mechanical coupling coefficients for various materials. Table 1 shows that the iron-based amorphous has the highest magneto-mechanical coupling coefficient. That is, the above-mentioned iron-based amorphous is suitable as the soft magnetic material used in the present invention.

[0018]

[Table 1]

Next, the impedance control will be described. Assuming that the electric resistivity of the soft magnetic film is ρ, the electric resistance of the soft magnetic film changes by a skin effect when an AC voltage is applied. Assuming that the skin thickness is δ, it is expressed by the following equation 3 with respect to the alternating current of the angular frequency ω.

[0020]

(Equation 3) The impedance Z of the soft magnetic film at this time is K = (1+
i) is given by the following equation 4 using the relationship of / δ.

[0021]

(Equation 4) Note that L and t are the length and thickness of the soft magnetic film, respectively. From equation (4), a change in the magnetic permeability appears as a change in the impedance of the soft magnetic film.

As described above, in the element having the composite structure of the piezoelectric material and the soft magnetic film, that is, the magnetostrictive material, the bending deformation generated by applying an external voltage to the piezoelectric thin film is sensed as the impedance change of the magnetostrictive thin film material. You can do it. Therefore, if there is a difference between the deformation amount determined from the impedance change and the target deformation amount, it is possible to maintain the desired deformation amount by controlling the voltage applied to the actuator. A distortion (stress) generated when the magnetic head or its supporting mechanism is displaced by an external force by incorporating the above-mentioned functional element in a part of a drive mechanism of a floating magnetic head functioning at a fixed distance from a magnetic disk.
Alternatively, the functional element detects the displacement and feeds it back to the drive voltage, whereby the positional relationship between the magnetic head and the magnetic disk can be controlled within a certain range.
In addition, the above-mentioned functional element is incorporated in a part of the drive mechanism of the contact type magnetic head which functions with a constant contact pressure with the magnetic disk, the magnetic head comes into contact with the magnetic disk, and the magnetic head or its support mechanism is displaced by an external force. The functional element detects the distortion (stress) or displacement generated in the case and feeds it back to the drive voltage, whereby the contact pressure between the magnetic head and the magnetic disk can be controlled within a certain range. As a result, even if there are minute irregularities on the surface of the magnetic disk, the force applied to the head can be equalized, and stable operation can be achieved. This can work equally well with either bulk or thin film materials.

[0023]

Next, an embodiment of the present invention and characteristics data will be described in comparison with comparative data with reference to FIGS. FIG. 1 shows an example in which a piezoelectric body and a magnetostrictive thin film are formed on an elastic substrate 1. In FIG. 1A, an electrode 2 is formed on one surface of an elastic substrate 1 and a PZT-based ceramic plate 3 which is a polarized piezoelectric material is bonded to form an actuator portion. This piezoelectric body may be a PZT-based piezoelectric thin film formed by a sol-gel method, a sputtering method, a CVD method, or the like. Then, an amorphous film 5, which is a magnetostrictive thin film, was formed thereon by sputtering via an SiO ₂ insulating film 4 to form a strain sensor portion. In FIG. 1B, PZ which is a piezoelectric material in which electrodes 2 are provided on both surfaces of an elastic substrate 1 respectively.
An actuator portion of a T-based ceramic plate 3 was provided, and an amorphous film 5 which was a magnetostrictive thin film was formed on one surface of the T-type ceramic plate 3 via an insulating film 4 by sputtering to form a strain sensor portion.

By connecting a power source to the actuator unit and controlling the direction of the applied voltage, the PZT-based piezoelectric body
As shown schematically in (A) and (B), it curves upward or downward. Note that in FIGS. 2A and 2B, the polarization direction of the piezoelectric ceramic is the ↑ direction on the paper. As a result, the magnetic permeability of the amorphous film 3 which is a magnetostrictive thin film formed on the elastic substrate 1 increases when a positive voltage is applied, and decreases when a negative voltage is applied. .
That is, since the magnetic permeability of the magnetostrictive thin film increases or decreases depending on the magnitude of the voltage, the bending of the element can be detected from the change in inductance. Here, the electrodes formed on the upper and lower surfaces of the PZT-based piezoelectric body can exhibit a function as an actuator even if they are formed not only in a flat plate shape but also in a cross finger shape.

Further, a specific example will be described. a External dimensions are 26mm long, 4mm wide, 0.1mm thick
Cr-Pt-Au on one side of a soft glass substrate of 5 mm
A 0.2 mm thick piezoelectric ceramic (Tokin brand name: N-
10) was adhered with an epoxy adhesive. 100 on this
After forming an insulating film of a SiO ₂ film having a thickness of 0, a high frequency magnetron sputtering device is further formed on the upper surface of the insulating film.
70.2% (atomic%, the same applies hereinafter), Fe, 7.8% C
o, an amorphous thin film serving as a magnetostrictive material having a composition of 12% Si and 10% B was formed to a length of 10 mm, a width of 400 μm, and a thickness of 2 mm.
A pattern was formed in a two-turn meander line shape of μm. The thickness of the film is 0.5 μm. The film formation conditions were an argon gas pressure of 25 × 10 ⁻³ torr and an output of 100 W, and the target was 72% Fe, 14% Si, 14% B in atomic%.
Was prepared while cooling the substrate with water using an alloy of Co and Co pellets. (b) PZT-based ceramics serving as a piezoelectric body was bonded to both surfaces of the substrate, and an amorphous thin film serving as a magnetostrictive material was formed on one surface of the substrate using a high-frequency magnetron sputtering device. The conditions are the same as the above a except that both sides are used.

The lead wires were joined to both ends of the pattern prepared as described above, and a network analyzer (HP 875) was used.
2A). A PZT-based ceramic plate that becomes a piezoelectric body with one end of a rectangular element fixed and the other end free is-
The impedance between the meander lines of the magnetostrictive film was measured while applying DC voltages of 80 V and +80 V. The result is shown in FIG. From the figure, when 500 MHz is applied, a maximum change of 17% was obtained in the case of reference numeral 6 and a maximum change of 8% was obtained in the case of reference numeral 7. 6 is the same as FIG.
Reference numeral 7 denotes the configuration of FIG. 1B, which is the case of the configuration of FIG. Next, the amount of deflection (deflection) of the rectangular element at this time was measured by an optical lever method, and the relationship between the amount of deflection and the invade was plotted. Note that, in this case, the measurement was performed on a material corresponding to the example of FIG. 1A in which a PZT-based ceramic serving as a piezoelectric body was adhered to one surface of a substrate. FIG. 4 shows the results. Clearly, it was confirmed that the amount of deflection and the change in inbidness were directly proportional.

A system is provided which feeds back the change in the impedance to the value of the drive voltage applied to the piezoelectric element. The principle of this system is that an inductance Z of a magnetostrictive element and a fixed resistor R are connected in series and connected to a low voltage power supply V, and that the voltage V1 across the inductance Z is proportional to the increase or decrease of the impedance. . Next, a reference voltage Vo is connected to one input terminal of the differential amplifier, and the above-described detection voltage V1 is input to the other input terminal. Since the output voltage of the differential amplifier is proportional to the difference voltage, this output is applied to the actuator element. That is, an increase or decrease in the amount of deflection is detected, and when the deflection increases, the voltage is decreased, and when the deflection decreases, the voltage is increased. The amount of voltage corresponding to a constant change in deflection was adjusted to an appropriate value according to the configuration conditions of the element. When a constant voltage of 20 V is applied to the control system to achieve a predetermined amount of bending of 100 μm, the change of the amount of bending displacement from the reference position over time is optically reflected when the control system is operated and when it is not operated. 20
Time was measured. The result is shown in FIG. When the control system does not work, the amount of bending displacement gradually increases with the passage of time (reference numeral 9), but when the control system is operated, the amount of bending displacement is maintained within a certain range (reference numeral 9). 8) was confirmed.

FIG. 6 shows an example in which the present invention is applied to a magnetic head unit 11 of a hard disk drive. The functional element of the present invention was formed in an arm portion 10 supporting a slider portion of a magnetic head. 0.3m thickness as arm material
m of phosphor bronze plate was used. On one surface of a phosphor bronze plate 12 having dimensions shown in FIGS. 7A and 7B, a Cr—Pt—Au sputtered film electrode is formed and subjected to polarization treatment to a 0.2 mm-thick piezoelectric ceramic plate 13 (Tokin product). (Name: N-10) was adhered to the positions shown in FIGS. 7 (A) and 7 (B), respectively. A SiO ₂ insulating film 14 is sputtered on the opposite side of the piezoelectric ceramic plate by 1000 sputtering, and 70.2% (atomic%, the same applies hereinafter) Fe, 12% Si, 10% by using a high-frequency magnetron sputtering apparatus. Using a mask of a magnetostrictive amorphous having a composition of B, a length of 10 mm and a width of 400 μm.
m, 2 μm thick and 2 turn meander line. The meandering line portion 15 is located substantially at the center. As shown in FIG. 8, the two devices were joined so that their surfaces were orthogonal to each other and soldered. The slider 16 of the magnetic head was bonded to the tip of the arm, and the opposite base was fixed to the fixing base 19 with a jig. Arm part 2
Two sets 17 and 18 of the displacement control system were constructed by combining the piezoelectric actuators and the flexural magnetostrictive sensors at several places. After applying a voltage of 30 V of each piezoelectric actuator section in the polarization direction, a time variation in a vertical direction and a horizontal direction with respect to the sliding surface of the head with respect to one point of the slider section,
The case where the displacement control system was activated and the case where it was not activated were observed using a television monitor-type tool microscope (× 100). The results are shown in the graph of FIG. If the displacement control system does not work, the vertical
In both the horizontal direction 22 and the horizontal direction, the amount of position fluctuation increases and changes over time in a fixed direction, but when the displacement control system works, the positions in the vertical 20 and horizontal 21 directions are kept constant. It was confirmed that the present invention was effective for position control of the magnetic head.

Next, as shown in FIG. 10, the load detector 25 of the load cell 24 was brought into contact with the magnetic head in a direction perpendicular to the slider-sliding surface, and was fixed at a portion where a load of 10 mg was applied. The load cell 24 has a function of oscillating with a minute amplitude of ± 20 μm in the load cell detecting direction.
It is fixed to 6. When the fixed base 26 of the load cell is vibrated sinusoidally with respect to time, the magnetic head and the load cell 2 are moved.
The contact pressure of No. 4 varies sinusoidally around 10 mg. FIG. 11 shows, in comparison with FIG. 11, changes in weight when the control system is not operated and when the control system is operated when the fixed base 26 is vibrated at 0.2 Hz. As is apparent from this result, when the control system is not operated, the amplitude of the contact weight is large and fluctuates greatly (reference numeral 27). In contrast, when the control system of the present invention was operated, the fluctuation of the contact load was small (reference numeral 28), and it was confirmed that the contact pressure of the magnetic head could be effectively controlled. In the above, the example using the PZT-based ceramic plate has been described. However, a thin film formed of a PZT-based piezoelectric material by a sol-gel method, a sputtering method, a CVD method, or the like has the same function as a bulk material.

[0030]

As described above, the functional element of the present invention is capable of self-detecting and controlling the amount of displacement by a simple combination of a laminated structure of an actuator made of a piezoelectric material and a strain sensor made of a magnetostrictive material. Function can be expressed. Therefore, it is effective in the field where control of minute displacement and control of minute contact pressure are required. In particular, a magnetic head equipped with this functional element enables fine control of the position of the sliding portion with respect to the recording medium and self-control of the contact pressure between the recording medium and the slider portion, thereby enabling the miniaturization and high recording density of magnetic recording. It can greatly contribute to improvement.

[Brief description of the drawings]

FIG. 1A is a functional element of the present invention in which a piezoelectric body and a magnetostrictive film are formed on one side, and FIG. 1B is a functional element of the present invention in which a piezoelectric body and a magnetostrictive film are formed on both sides.

FIG. 2 is a schematic diagram showing an applied voltage and a direction of element deformation.

FIG. 3 is a graph showing the relationship between the applied voltage and the rate of change of impedance.

FIG. 4 is a graph showing the relationship between the amount of deflection displacement and the rate of change of impedance.

FIG. 5 is a graph showing the change over time of displacement with and without a control function.

FIG. 6 is a schematic explanatory view of a magnetic head of a hard disk drive (HDD).

FIGS. 7A and 7B are partial schematic illustrations of an arm portion.

FIG. 8 is a conceptual diagram showing an example of an arm unit to which the present invention is applied.

FIG. 9 is a graph showing variations in the horizontal and vertical positions of a magnetic head sliding portion with and without a control function.

FIG. 10 is a load test apparatus for performing a contact load test by contacting a load detector of a load cell in a direction perpendicular to a slider-sliding surface of a magnetic head.

FIG. 11 is a graph showing a change in weight with time when the control system is not operated and when the control system is operated.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Elastic substrate 2 Electrode 3 Piezoelectric ceramic 4 Insulator film 5 Amorphous film 10 Arm part 11 Head sliding part 12 Phosphor bronze (elastic body) substrate 13 Piezoelectric ceramic (with electrode) 14 Insulator film 15 Amorphous (magnetostrictive) pattern Reference Signs List 16 Magnetic head sliding portion (slider) 17 Displacement element with sensor (FIG. 7 (A)) 18 Displacement element with sensor (FIG. 7 (B)) 19 Fixing jig 24 Load cell 25 Load cell weight detection section 26 Load cell drive mechanism

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kenichi Arai 2-28-9 Yamanoji Temple, Izumi-ku, Sendai City, Miyagi Prefecture (72) Inoue Mitsuru 2-3-10 Mukaiyama, Taishiro-ku, Sendai City, Miyagi Prefecture Villamar Mukoyama 102 (72) Inventor Etsuo Otsuki 6-7-1, Koriyama, Taihaku-ku, Sendai City, Miyagi Prefecture, Japan (72) Inventor Mitsuo Tamura 6-7-1, Koriyama, Tajiro-ku, Sendai City, Miyagi Prefecture Tokinnai, Inc. ( 72) Inventor Junji Tani 1-5-11, Toromachi, Aoba-ku, Sendai City, Miyagi Prefecture

Claims (7)

[Claims] 1. A piezoelectric material functioning as an actuator element and a magnetostrictive material having a sensor function are laminated, and a displacement due to distortion or deformation of the piezoelectric material is detected by the magnetostrictive material and converted into an electric signal. A functional element comprising a composite layer of a magnetostrictive material and a piezoelectric material, wherein the displacement of the laminate is corrected by feeding back to a control voltage of the material. 2. A method according to claim 1, wherein one or a plurality of piezoelectric materials functioning as actuator elements and a plurality of magnetostrictive materials having a displacement sensor function are formed in a part of a drive mechanism of the contact type magnetic head which functions with a constant contact pressure with the magnetic disk. By detecting the distortion or deformation of the piezoelectric material caused by contact with the magnetic disk by the magnetostrictive material and converting it into an electric signal, and feeding it back to the actuator of the piezoelectric material to correct the displacement of the piezoelectric material, The magnetic head is brought into contact with the magnetic disk with a constant contact pressure, and / or the position of the magnetic head is finely controlled in the horizontal direction with respect to the magnetic disk by the displacement due to the distortion or deformation of the piezoelectric material. The deviation from the standard is detected by the magnetostrictive material and converted into an electric signal, which is By correcting the displacement of the piezoelectric material by feeding back to the data, the positional relationship between the magnetic head and the track on the magnetic disk surface is finely adjusted. From the composite layer of the magnetostrictive material and the piezoelectric material, Magnetic head having a functional element. 3. One or a plurality of piezoelectric materials functioning as actuator elements and one or more magnetostrictive materials having a displacement sensor function are formed in a part of a drive mechanism of a floating magnetic head functioning at a fixed interval from a magnetic disk. At the same time, the position of the magnetic head is finely controlled in the vertical and / or horizontal direction with respect to the magnetic disk by the displacement due to the distortion or deformation of the piezoelectric material, and at the same time, the deviation of the displacement from the reference is detected by the magnetostrictive material and converted into an electric signal. Converting the data and feeding it back to an actuator made of a piezoelectric material to correct the displacement of the piezoelectric material, thereby finely adjusting the distance between the magnetic head and the recording medium and / or the positional relationship with the track in the magnetic disk surface. A magnetic head comprising a functional element comprising a composite layer of a magnetostrictive material and a piezoelectric material, characterized in that: 4. The functional element according to claim 1, wherein the piezoelectric material and / or the magnetostrictive material is a bulk material. 5. The functional element as claimed in claim 1, wherein the piezoelectric material and / or the magnetostrictive material is a thin film. 6. The functional element according to claim 1, wherein the magnetostrictive material is an amorphous material of a Fe—Co—Si—B-based alloy. 7. The functional element according to claim 1, wherein a displacement due to distortion or deformation of the piezoelectric material is detected by a magnetostrictive material using a high-frequency carrier of 1 MHz to 2 GHz. A magnetic head including the functional element.