WO2007012672A1

WO2007012672A1 - Method of producing a layer-substrate composite and layer-substrate composite

Info

Publication number: WO2007012672A1
Application number: PCT/EP2006/064808
Authority: WO
Inventors: Sebastian Fähler; Karin Leistner; Volker Neu
Original assignee: Leibniz-Institut Für Festkörper- Und Werkstoffforschung Dresden E.V.
Priority date: 2005-07-29
Filing date: 2006-07-28
Publication date: 2007-02-01
Also published as: DE102005036682B4; DE102005036682A1

Abstract

The invention concerns the field of physics and relates to a method of producing a layer-substrate composite, such as can be used for example for high-power magnets in magnetic, microstructured components. The object of the present invention is to provide a low-cost method and a layer-substrate composite of a texturing that is largely independent of the substrate. The object is achieved by a method in which a layer to be textured, which contains components for forming a layer with hard-magnetic properties, is applied to a substrate and compressive or tensile stresses are introduced into the layer during the application of the layer or thereafter. The object is further achieved by a layer-substrate composite comprising a substrate and at least one layer to be textured, which contains components for forming a layer with hard-magnetic properties, the layer having a state of stress comprising compressive or tensile stresses.

Description

Process for producing a layer-substrate composite and layer-substrate composite

The invention relates to the field of physics and magnetic materials and relates to a method for producing a layer-substrate composite, as used for example for high-performance magnets in magnetic, microstructured components, such as electromagnetic motors, actuators or sensors, and the magnetic data storage can.

In order to make more efficient use of the excellent hard magnetic properties of modern high-performance magnets (based on Nd-Fe-B, Sm-Co, Fe-Pt, Fe-Pd, Co-Pt), the magnetic materials are texturized. In such texturing, the magnetically easy axis, which is parallel to the crystallographic c-axis for these high-performance magnets, is aligned along the direction of application. Such texturing allows a doubling of the remanence and thus a quadrupling of the energy product BH _max compared to isotropic, not exchange-coupled permanent magnet. With textured permanent magnets therefore much smaller, and thus more efficient electromagnetic motors and actuators can be built.

The texturing is particularly important for magnetic Micro Electro Mechanical Systems (MEMS like) is important, which are not built from solid material but from layers (S.Fähler, ^th inter alia 18 Int. Workshop on high performance magnets and their applications 2 (2004) 566).

Texturing is also beneficial for magnetic data storage. By texturing the c-axis perpendicular to the substrate, the storage density can be further increased within the scope of the perpendicular recording (M. Plumer et al. (Edn.), The Physics of Ultra-High-Density Magnetic Recording, Springer Series in Surface Sciences Vol , Springer-Verlag Berlin (2001)).

So far, texturing could be done on layers

I) a growth texture,

II) epitaxy,

IM) recrystallization or

IV) Ion Beam Assisted Deposition (IBAD) (US 2004 0248743).

In these cases, texturing is often achieved via a buffer (US 2004

0058196).

The methods I-IV have some disadvantages.

Thus, a suitable, often expensive substrate must be used or additional, complex equipment is required (eg in IBAD). When the texture is communicated through the substrate or buffer, a textured grain generally grows continuously from the substrate to the surface. However, especially for thick layers, as required for mag-MEMS, the grains become so large that it becomes difficult to achieve a high coercive field. In addition, a structurally unfavorable, high roughness can arise (U. Hannemann, et al., IEEE Trans. Mag. 38 (5) (2002) 2805).

By a combination of texturing and exchange coupling (EF Kneller, et al., IEEE Trans. Mag. 27 (1991) 3588) in highly anisotropic / highly remanent layer packages, a significant increase of the energy product over the previously achieved values is possible (R. Skomski, J. Appl. Phys., 76 (10) (1994) 7059). With the texturing methods I-IV, however, only thin, two-ply Layer structures can be realized because the texture of the hard layer is lost in multi-layer systems.

Only EE Fullerton, et al J. Mag. Mat. 200 (1999) 392 previously textured, exchange-coupled multilayers have been achieved exclusively for the system Sm ₂ Co ₇ / Co. However, this material combination is uninteresting with respect to the achievable energy product for a practical application.

Furthermore, it is known from the prior art that in massive FePd samples by applying an external pressure almost complete texturing of the magnetically highly anisotropic, ordered LI ₀ phase can be achieved (K. Tanaka, et al., J. Mag. Mag. Mat 200 (1999) 392). The system avoids the external constraint by aligning the shorter, magnetically light axis in the direction of the external pressure. Texturing reduces the overall energy of the system, an effect that is effective in both the nucleation phase and the growth phase of the LI ₀ phase.

Voltages can also be applied by different coefficients of thermal expansion of the layer and substrate and by the layer growth (P. Rasmussen et al., Appl. Phys. Lett., 86 (2005) 191915). However, these stresses are limited so that only very low levels of textures are achieved with this method (orientation coefficients K * = 0.829). In addition, the choice of the substrate is limited by the choice of a suitable coefficient of expansion and can not be done from an economic point of view. The solution described by Rasmussen also assumes the metastable fcc starting state. In polycrystalline layers, grains whose elementary cell is oblique to the strain do not have a simple tetragonal distortion. Thus, sufficient texturing is not achievable.

The object of the present invention is to specify a cost-effective method for producing a layer-substrate composite whose texturing is largely independent of the substrate.

In the method according to the invention for the production of a layer-substrate composite, at least one layer to be textured, which is at least the Contains components for forming a layer with hard magnetic properties, applied to a substrate and during the layer application or after the compressive or tensile stresses are introduced into the layer.

Advantageously, two layers to be textured or a multiple layer of two repeating layers to be textured are applied.

Also advantageously, a stress is generated in the layers to be textured during film formation.

Further advantageously, the substrate is mechanically clamped during the layer application and relaxed before a heat treatment.

It is also advantageous if mechanical stresses are generated in the layer material during the heat treatment.

It is also advantageous if the substrate is subjected to tensile stress or bending stress during the heat treatment.

It is furthermore advantageous if a metallic or polymeric substrate is used.

It is also advantageous if mechanical stresses are generated extrinsically or intrinsically.

It is also advantageous if a partial stress relief in the layers and / or the substrate is realized by a heat treatment or an ion irradiation.

And it is also advantageous if the phases located in the layers to be textured are deposited in the amorphous state.

It is also advantageous if the phases in the layers to be textured are deposited in a cubic crystal symmetry. It is furthermore advantageous if the layer production is carried out by means of sputter deposition, thermal evaporation, pulsed laser deposition, electrochemical deposition or sol-gel processes.

And it is also advantageous if the layer preparation is carried out in an atmosphere which contains or consists of H and / or O and / or N and / or noble gases, the layer preparation is carried out in the presence of solvents and / or materials with high vapor pressure or the layer preparation in the presence of water, organic solvents, halogens and / or Mn, Sm, Ga, In, B is performed.

It is furthermore advantageous if the ion irradiation is carried out with light ions.

It is likewise advantageous if ion irradiation with He ^{+ is} carried out during or after the layer production.

It is also advantageous if a heat treatment is carried out in the range of 250 to 900 ^° C. depending on the hard magnetic phases used in each case, the heat treatment is carried out under a reducing, hydrogen-containing atmosphere, or the heat treatment for the conversion of a component in the textile to be textured Layer with high crystal symmetry in a component with magnetically highly anisotropic properties and tetragonal or hexagonal crystal symmetry is performed.

It is also advantageous if the tension in the layer to be textured is set by the extraction of at least one component.

In a further inventive method for producing a layer-substrate composite having hard magnetic properties is a layer to be textured, which contains at least the components for forming a layer with hard magnetic properties and not yet in the tetragonal L1 ₀ Equilibrium state (c / a <1), applied to a substrate and placed in a stress state of compressive or tensile stresses during or after the coating application, followed by heat treatment or ion irradiation to convert the components of the hard magnetic phase forming layer into the tetragonal ones L1 ₀ equilibrium state (c / a <

, , , , .... Comment [kli:

1).

After the application of two layers to be textured, a heat treatment is advantageously carried out and subsequently two further layers to be textured are applied to the already heat-treated layers and subsequently a heat treatment is carried out and this sequence is repeated one or more times.

Also advantageously, tensile stresses are generated in all applied layers to be textured and compressive stress in the substrate.

The layer-substrate composite according to the invention consists of a substrate and at least one layer to be textured which contains at least the components for forming a layer having hard-magnetic properties, wherein the layer has a stress state of compressive or tensile stresses.

It is advantageous if two layers to be textured are present on the substrate.

It is also advantageous if a multi-layer to be textured of at least two repeating layers is present.

It is also advantageous if one layer of the multilayer contains components for forming a magnetically highly anisotropic phase and the other layer contains components for forming a ferromagnetic material with a high remanence.

It is also advantageous if the layer to be textured FePt, CoPt, FePd, Nd-Fe-B, Pr-Co and / or Sm-Co as components for forming a layer with contains hard magnetic properties or when in the layer to be textured as components for forming a ferromagnetic material with a high remanence Fe-Co, Fe, Fβ ₃ Pt and / or Fe-B are included, wherein still advantageously one of the layers to be textured, the Contains components for the formation of hard magnetic phases, has a higher crystal symmetry, as the magnetically highly anisotropic phase.

The texturing according to the invention is based on the combination of two steps, which can be realized by different procedures. First, the layer material from which the hard magnetic phase is to be formed is prepared in an intermediate state (metastable state) as a layer in which the atomic order (crystal symmetry in crystalline phases) still deviates from the desired hard magnetic phase in the final state. Subsequently, the conversion of this layer from the metastable state into a layer having the desired hard magnetic phase under the action of a heat treatment and at the same time acting voltages is performed. The stresses can either be applied externally, or arise through the corresponding application of the layers and / or by the heat treatment in the system itself (internally). As a result of these two steps, a texture sets in the hard magnetic layer. The described method shows how the voltages can be introduced independently of the selected substrate. If it is assumed that the amorphous state, even higher levels of textural can be achieved.

This basic procedure is illustrated below by way of example on electrodeposited FePt layers, but can easily be extended to other material systems and ways of implementation by a person skilled in the art.

When electrodeposition of FePt from aqueous solutions significant amounts of oxygen in the form of Fe-OH phases (up to 30 at.% O) are introduced into the layer. After production, the layers are amorphous (ie no direction is excellent). In the subsequent heat treatment (aging), which leads to the formation of the highly anisotropic LI ₀ phase (with an excellent Symmetry axis) is necessary, the oxygen content can be reduced to below 10 at.% By the use of a reducing, hydrogen-containing atmosphere (K. Leistner et al. J. Mag. Mag. Mat. 280-291 (2005) 1270). The associated volume reduction leads on the one hand to a significant decrease in the layer thickness and on the other hand to high tensile stresses, since the applied layer (1-50 microns) is generally much thinner than the substrate (0.5 -2 mm) and is therefore fixed on this , The simultaneous conversion of the metastable amorphous into the tetragonal LI ₀ equilibrium phase (c / a <1) during the heat treatment offers the possibility of texturing in the context of the solution according to the invention. Due to the intrinsic tensile stresses, the longer a, b axes align preferentially in the film plane and consequently the shorter, magnetically gentle c axis perpendicular to the substrate surface. The entire magnetic moment is then available in this application direction.

A decisive advantage of this solution according to the invention is that the texturing is largely independent of the substrate, so that substrates with more favorable mechanical properties and lower costs can be selected. Since the texturing is not distributed over the substrate but evenly over the layer and thus produced locally, it is also possible to produce textured, exchange-coupled layer packages (multilayers). In applying the layers by electrodeposition, the change in the applied voltage allows the composition to be adjusted so that layer packages of FePt and Fe (or alternatively, Fβ ₃ Pt) can be made. The heat treatment results in a textured, exchange-coupled layer package, in which the high coercive field of the FePt layer ordered by L1 ₀ and the high remanence of the Fe (or alternatively Fβ ₃ Pt) layer results in a significantly higher energy product than in a single layer.

The presented solution principle according to the invention can be transferred to a multiplicity of systems.

The requirement of a change in crystal symmetry by heat treatment (aging) is also fulfilled for the highly anisotropic Nd-Fe-B and Sm-Co phase, when the layers grow amorphous in the first step of the preparation (by Deposition on unheated substrates) and only during a heat treatment at some 100 ⁰ C to convert into their highly anisotropic equilibrium phase.

The introduction of the stress during the heat treatment (aging) is possible in various ways, which are described below by way of example.

For rare earth magnets, an increase in volume can be achieved by deposition under a hydrogen-containing atmosphere. This is also advantageous because the influence and extraction of hydrogen in these systems is well understood in the context of the HDDR process and is associated with a large volume change. As extractables, all gases (H, O, N, noble gases), solvents (water, organic solvents, halogens) and / or materials with high vapor pressure (Mn, Sm, Ga, In, B) can be used, which during the Apply first in the layer to be incorporated, but only weak bonds enter, therefore, dissolve again as a result of the heat treatment.

In addition to the physical deposition methods, which allow a simple incooperation of gases and solids, especially efficient chemical deposition methods are available (electrode position, sol-gel method, etc.), in which solvent constituents can be used.

In addition to intrinsic stresses, extrinsic stresses can also be generated by placing the layers under external stress during the heat treatment. This can be done in different ways and is advantageously carried out on metallic or polymeric or elastomeric substrates.

For example, the substrates are mechanically stressed during the heat treatment.

In the case of a uniaxial tensile stress, the longest crystallographic axis aligns with the external force. Thus, for c / a> 1 uniaxial texturing can be achieved with the magnetically easy axis (c-axis) within the layer plane. For c / a <1, a uniaxial tensile stress causes the shorter axis is aligned perpendicular to the applied voltage. Due to this texture, the remanent magnetization reaches up to 64% of the

Saturation magnetization (instead of a maximum of 50% for isotropic microstructure).

If the substrate is exposed to a biaxial tensile stress, complete alignment of the short c-axis perpendicular to the substrate plane is also possible for c / a <1.

It is also possible to clamp the substrates during the layer deposition and to relax before the heat treatment. Thus, after the production of the layer structure, the stresses are transferred to the layers and have a texture-forming effect during the heat treatment (aging). If a substrate is placed under a uniaxial tensile stress during deposition, uniaxial compressive stresses within the layer plane occur after deposition. During the heat treatment, for c / a <1 this again leads to a complete alignment of the c-axis along this direction.

Instead of putting the substrate under a pure tension, it can also be bent (eg on a 4-point overlay). After coating and relaxation of the substrate, tensile stress acts on one substrate side (the inside of the bend) and compressive stresses on the other substrate side (the outside of the bend) on the layer. With this structure, so both tensile stresses and compressive stresses can be realized - depending on the choice of the substrate side during the coating.

A further alternative possibility of generating stresses in the layers is achieved by ion implantation of noble gases, whereby compressive stresses arise due to the additional ions in the layer. If this compressive stress exceeds the yield strength, plastic deformation occurs. In a subsequent heat treatment, the mobility of the implanted ions increases and insoluble noble gas ions can diffuse out of the layer. As a result, the pressure changes to tensile stresses and the shorter axis is perpendicular to the substrate. Unordered layers of FePt, FePd or CoPt can also be irradiated with light ions (eg He ⁺ ) in the solution according to the invention, whereby an order adjustment without heat treatment at higher temperatures is achieved. Thus, at the same time as the order setting, a texture can be achieved in which the shorter axis lies in the layer plane. In addition to a simpler process management, the grain growth, which is undesirable in magnetic data storage in particular, can be avoided, which can occur at higher heat treatment temperatures.

Also, methods such as pulsed laser deposition and ion beam deposition methods are promising, since the high-energy ion content leads to subplantation and thus to high compressive stresses already during layer production.

The invention will be explained in more detail below with reference to several exemplary embodiments.

example 1

An amorphous layer of FePt with a layer thickness of 700 nm is applied to a substrate of Si with W-Ti buffer with the dimensions 10 × 20 mm. Subsequently, a heat treatment at 600 ⁰ C is carried out in a hydrogen atmosphere. Reducing the Fe hydroxides reduces the volume by 15%, resulting in tensile stresses in the 2 gigapascal layer.

After the heat treatment, a layer-substrate composite is present, with the light axis layer textured perpendicular to the substrate plane. A pretreatment of the substrate to achieve or improve the texturing of the layer is not required.

Example 2

A layer of CoPt with a layer thickness of 5 μm is applied by means of a sol-gel process to a 0.5 mm thick, glass substrate with dimensions of 100 × 50 mm, polished on both sides. The layer on the substrate is now externally subjected to a tensile stress by the middle area of 50 mm supported by two bars and the short sides are pulled down. The elongation of the substrate surface is thus adjusted to 2%. In this state of stress, the substrate with the layer is subjected to a heat treatment at 600 ^° C. for 60 minutes.

After the heat treatment, a layer-substrate composite is present, the layer being largely textured. A pretreatment of the substrate to achieve or improve the texturing of the layer is not required.

Example 3

On a Si substrate with 1 mm thickness, 3 "diameter and with a 30 nm thick Ta buffer are sputtered by an amorphous layer of Nd-Fe-B with a layer thickness of 10 nm and then a layer of Fe-Co with a layer thickness Each layer is applied alternately 99 times, so that a multilayer layer of 100 layers is present, and the entire layer is covered with 30 nm Cr.

Ar ions are introduced into this multilayer layer by means of ion implantation, which place the layer under compressive stresses, whereupon plastic deformation takes place. Subsequently, a heat treatment at 650 ⁰ C for 5 minutes, whereby the implanted Ar ions diffuse out of the multilayer layer out again and thus put the layer under tension. After the heat treatment, a layer-substrate composite is present, wherein the layer is textured and the original layer architecture remains largely intact. A pretreatment of the substrate to achieve or improve the texturing of the layer is not required.

Claims

claims

Anspruch [en] A process for producing a layer-substrate composite in which at least one layer to be textured which contains at least the components for forming a layer having hard-magnetic properties is applied to a substrate and printed or coated in or after the layer application Tensile stresses are introduced.

2. The method of claim 1, wherein two layers to be textured or a multiple layer of two repeating layers to be textured are applied.

3. The method of claim 1, wherein in the layers to be textured during the layer production, a voltage is generated.

4. The method of claim 1, wherein the substrate is mechanically clamped during the layer application and relaxed before a heat treatment.

5. The method of claim 1, wherein during the heat treatment, mechanical stresses are generated in the layer material.

6. The method of claim 1, wherein the substrate is set during the heat treatment under tensile stress or bending stress.

7. The method of claim 1, wherein a metallic or polymeric substrate is used.

8. The method of claim 1, wherein the mechanical stresses are generated extrinsically.

9. The method of claim 1, wherein mechanical stresses are generated intrinsically.

10. The method of claim 1, wherein a partial stress relief in the layers and / or the substrate by a heat treatment or ion irradiation is realized.

11.A method according to claim 1, wherein the phases located in the layers to be textured are deposited in the amorphous state.

12. The method of claim 1, wherein the phases in the layers to be textured are deposited in a cubic crystal symmetry.

13. The method of claim 1, wherein the layer production by sputter deposition, thermal evaporation, pulsed laser deposition, electrochemical deposition or sol-gel method is performed.

14. The method of claim 1, wherein the layer preparation is carried out in an atmosphere containing H and / or O and / or N and / or noble gases or consists thereof.

15. The method of claim 1, wherein the layer preparation is carried out in the presence of solvents and / or high vapor pressure materials.

16. The method of claim 1, wherein the layer preparation in the presence of water, organic solvents, halogens and / or Mn, Sm, Ga, In, B is performed.

17. The method of claim 1, wherein the ion irradiation is performed with light ions.

18. The method of claim 1, wherein during or after the layer preparation, ion irradiation with He ^{+ is} performed.

19. The method according to claim 1, wherein a heat treatment in dependence on the particular hard magnetic phases used in the range of 250 to 900 ⁰ C is performed.

20. The method of claim 1, wherein the heat treatment is carried out under a reducing, hydrogen-containing atmosphere.

21. The method of claim 1, wherein the heat treatment for converting a component in the high crystal symmetry layer to be textured into a component having magnetically highly anisotropic properties and tetragonal or hexagonal crystal symmetry is performed.

22. The method of claim 1, wherein the tension is set in the layer to be textured by the extraction of at least one component.

23. A method for producing a layer-substrate composite having hard magnetic properties, wherein a layer to be textured, which contains at least the components for forming a layer with hard magnetic properties and not yet in the tetragonal LI ₀ equilibrium state (c / a <1 ), applied to a substrate and subjected to compressive or tensile stress state during or after the layer application, followed by heat treatment or ion irradiation to convert the components of the hard magnetic phase layer to the tetragonal LI ₀ equilibrium state (c / a <1) is performed.

24. The method of claim 1 or 23, wherein after the application of two layers to be textured, a heat treatment is carried out and subsequently two more layers to be textured are applied to the already heat-treated layers and subsequently in turn a heat treatment is performed and this process one or more times is repeated.

25. The method of claim 1 or 23, wherein in all applied layers to be textured tensile stresses and in the substrate compressive stress is generated.

26. A layer-substrate composite produced according to at least one of claims 1 to 25, comprising a substrate and at least one layer to be textured, which contains at least the components for forming a layer with hard magnetic properties, wherein the layer has a stress state from or tensile stresses.

27. The composite of claim 26, wherein two layers to be textured are present on the substrate.

28. The composite of claim 26 wherein there is a multi-layer of at least two repeating layers to be textured.

29. The composite of claim 28, wherein one layer of the multilayer contains components for forming a magnetically highly anisotropic phase and the other layer contains components for forming a ferromagnetic material having a high remanence.

A composite according to claim 26, wherein the layer to be textured contains FePt, CoPt, FePd, Nd-Fe-B, Pr-Co and / or Sm-Co as components for forming a layer having hard magnetic properties.

A composite according to claim 29, wherein Fe-Co, Fe, Fe ₃ Pt and / or Fe-B are contained in the layer to be textured as components for forming a high-remanence ferromagnetic material.

32. The composite according to claim 27 or 28, wherein one of the layers to be textured containing the components for forming the hard magnetic phases has a higher crystal symmetry than the magnetically highly anisotropic phase.