System for the production of ε-phase MnAl and Co bilayer thin films

Abstract

A system for the fabrication of ε-phase MnAl / Co bilayer thin films, consisting of: a) a high-frequency magnetron sputtering system for the deposition of multilayer thin films on a silicon substrate, the sputtering system comprising: • a system for maintaining base pressure, configured to maintain a constant pressure; • three 2-inch targets consisting of MnAl, Co and Ta; and • a substrate rotation mechanism configured to rotate the substrate at a constant number of revolutions per minute; b) a layer deposition unit that is operationally connected to the RF magnetron sputtering system and enables the sputtering system to deposit layers sequentially: • a 3 nm thick Ta buffer layer on the silicon substrate; • a 60 nm thick MnAl layer on the Ta buffer layer; • a Co layer with a thickness of 1 nm to 5 nm on the MnAl layer; and • a 5 nm thick Ta top layer on the Co layer; c) an annealing furnace configured to anneal the deposited Ta and MnAl layers for 2 hours at 600 °C before the Co layer is deposited; and d) a characterization unit for analyzing the produced thin films, wherein the characterization unit comprises the following: • an X-ray diffraction (XRD) system for structural characterization; • an optical 3D profilometer for measuring surface structure and mean roughness; and • a field emission scanning electron microscope (FESEM) with energy-dispersive X-ray spectrometer (EDS) for analyzing surface morphology and elemental composition.

Description

AREA OF INVENTION

[0001] The present disclosure relates to a system for the production of ε-phase MnAl / Co bilayer thin films. In particular, the present invention relates to a system for the production of ε-phase MnAl / Co bilayer thin films and the investigation of their magnetic properties. BACKGROUND OF THE INVENTION

[0002] Permanent magnets (PMs) are indispensable in a wide variety of industries, including electrical appliances, computers, consumer electronics, power generators, wind turbines, electric vehicles, and medical technology. For example, the transition of the transportation sector from internal combustion engines to electric vehicles (EVs) is expected to rapidly increase the demand for permanent magnets. Consequently, significant progress was made in improving their properties during the 20th century. The ability of PMs to maintain a high magnetic flux in their respective application environment, even without an applied magnetic field, is their most outstanding characteristic and makes them essential for the aforementioned applications. High coercivity (Hc) and magnetic flux density (Br), as well as the maximum energy product (BH), are key factors in their performance. max These are crucial properties of PM materials. The maximum energy product (BH) maxProvides an estimate of the magnetic flux density that a permanent magnet can store. PMs with high BH max High performance and thermal stability are particularly in demand for demanding applications.

[0003] NdFeB magnets dominate the market due to their excellent magnetic properties. However, their production is heavily dependent on the availability of rare earth elements (REEs). REEs, particularly neodymium (Nd), dysprosium (Dy), and terbium (Tb), are in high demand for the production of high-performance permanent magnets used in virtually all modern technologies. Global REE production is highly concentrated, with China supplying the majority of the market. This concentration creates economic risks such as price fluctuations and supply chain disruptions.

[0004] The high cost of rare-earth elements makes the commercial use of high-performance magnets very expensive. Given the increasing demand for permanent magnet technology and the limited global availability of rare-earth elements, the need for rare-earth-free (REF) magnets is becoming increasingly apparent. Among the potential alternatives, iron-based REF magnets, especially ferrites, are inexpensive and manufactured from readily available raw materials; however, their magnetic performance is limited by a low maximum energy product (BH). Promising candidates such as α-Fe 16 N2 and tetrataenite (FeNi) have emerged as key materials, but challenges in the synthesis of polycrystalline materials or the production of mass magnets have hampered their development so far.

[0005] In contrast, manganese-based magnets are easier to manufacture and less expensive, making them viable alternatives to rare-earth and cobalt-based magnets for consumer applications and medium-power motors. Manganese-based compounds exhibit promising magnetic properties, ease of production, and abundant occurrence in the Earth's crust—all at significantly lower costs than rare-earth-based magnets. Researchers are particularly interested in manganese alloys such as MnAl, MnGa, and MnBi as potential candidates for rare-earth-free permanent magnets due to their strong magnetic anisotropy. Among manganese-based magnets, MnAl alloys are considered a promising material for rare-earth-free permanent magnets because of their significant magnetocrystalline anisotropy and theoretical maximum energy product of 16.8 MGOe.

[0006] Manganese (Mn) is a useful and, due to its four allotropic forms (α, β, γ, and δ phases), one of the most complex metallic elements. When Mn is alloyed with aluminum (Al) at different temperatures and atomic concentrations, the resulting binary alloy system MnAl consists of various phases. MnAl alloys exhibit several key phases, most notably the stable, non-magnetic ε phase (hexagonal close-packed – hcp) and the metastable, hard-magnetic τ phase (tetragonal), which forms from the ε phase via an intermediate ε phase through complex transformations and is crucial for permanent magnets. Other stable phases, such as β and γ₂ (e.g., Al₈Mn₅), also coexist, depending on the composition and processing techniques (milling, annealing). Köno first discovered and described the intrinsic ferromagnetic properties of Mn-Al compounds in 1958.Using X-ray diffraction analysis and magnetic measurements, he made the groundbreaking discovery of a metastable ferromagnetic phase in the Mn-Al system in the composition range of 47–60% Mn. By carefully cooling the hexagonal close-packed (hdp) structure, Köno found that a metastable tetragonal CuAu phase (L10) occurs. According to the Bethe-Slater curve, this phase possesses ferromagnetic properties and a Curie temperature of approximately 370 °C. A promising approach to increasing the coercive field strength and energy product is the fabrication of hard-soft bilayers. Through magnetic exchange coupling, the maximum energy product (BH) could be achieved. max ) of MnAl. In magnetically exchange-coupled magnets, both hard and soft phases are present. These utilize the high coercivity of the hard phase and the high magnetization of the soft phase to achieve the maximum coercivity (BH).max ) compared to the purely hard phase. Improved hard and soft magnets are therefore essential for next-generation technologies, according to manufacturers and users worldwide.

[0007] Most studies focus on the τ-phase of MnAl alloys, leaving little information on the ε-phase of MnAl alloys and their bilayers. The ε-phase itself is typically antiferromagnetic or paramagnetic at room temperature and therefore unsuitable for direct use as a permanent magnet. It generally exhibits very low magnetization and virtually no coercivity until it is transformed into the τ-phase. However, the ε-phase is utilized in material processing to produce rare-earth-free permanent magnets. Therefore, it is crucial to understand the properties of the MnAl alloy in the ε-phase and to fabricate bilayers with magnetic elements to evaluate their magnetic properties and potential applications. SUMMARY OF THE INVENTION

[0008] The present invention provides a system for the fabrication of ε-phase MnAl / Co bilayer thin films with enhanced magnetic properties. This invention relates to a bilayer structure of Ta (3 nm) / MnAl (60 nm) / Co (x nm) / Ta (5 nm), where x varies from 1 to 5 nm, produced by RF magnetron sputtering. The invention is particularly characterized by the integration of an ultrathin Co layer, which significantly improves the saturation magnetization, coercivity, and overall magnetic properties through strong exchange coupling with MnAl. The Ta top layer provides effective protection against oxidation, thus ensuring the long-term preservation of the magnetic properties. By adjusting the Co layer thickness, the invention enables tunable magnetic behavior tailored to specific device requirements. Overall, this invention relates to the fabrication of...The ε-phase of MnAl / Co bilayer thin films is investigated to understand their magnetic properties, which are relevant for spintronics applications, magnetic storage components, and rare-earth-free permanent magnets.

[0009] The present disclosure relates to a system for the fabrication of ε-phase MnAl / Co bilayer thin films. The system comprises: a) a high-frequency magnetron sputtering system for the deposition of multilayer thin films on a silicon substrate, the sputtering system comprising: a base pressure maintenance system for maintaining a pressure of 3.99 × 10 -6kPa; three 2-inch targets made of MnAl, Co, and Ta; and a substrate rotation mechanism for rotating the substrate at 30 revolutions per minute; b) a layer deposition unit connected to the high-frequency magnetron sputtering system, enabling the sputtering system to sequentially deposit: a 3 nm thick Ta buffer layer on the silicon substrate; a 60 nm thick MnAl layer on the Ta buffer layer; a Co layer with a thickness of 1 nm to 5 nm on the MnAl layer; and a 5 nm thick Ta top layer on the Co layer; c) an annealing unit for annealing the deposited Ta and MnAl layers at 600 °C for 2 hours prior to deposition of the Co layer; and d) a characterization unit for analyzing the fabricated thin films, the characterization unit comprising: an X-ray diffraction (XRD) system for structural characterization; a 3D optical profilometer for measuring surface topography and mean roughness;and a field emission scanning electron microscope (FESEM) with energy-dispersive X-ray spectrometer (EDS) for analyzing surface morphology and elemental composition.

[0010] The subject of the present disclosure is the provision of a system for the production of ε-phase MnAl / Co double-layer thin films.

[0011] Another subject of the present disclosure is the production of ε-phases of MnAl alloys by means of RF magnetron sputtering.

[0012] Another objective of the present disclosure is the fabrication of ε-phase thin films from MnAl / Co double layers in order to understand their magnetic properties.

[0013] Another objective of the present disclosure is the characterization of the produced double-layer thin films.

[0014] Another objective of the present disclosure is to provide ε-phase thin films made of MnAl / Co bilayers, which are well suited for advanced electronic systems, energy-efficient actuators and compact magnetic components used in industrial and consumer applications.

[0015] To further clarify the advantages and features of the present disclosure, the invention is described in more detail with reference to specific embodiments illustrated in the accompanying drawings. It is understood that these drawings merely show typical embodiments of the invention and are therefore not to be understood as limiting its scope of protection. The invention is described and explained in more detail and with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE IMAGES

[0016] These and other features, aspects and advantages of the present disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings, in which identical symbols represent identical parts, wherein: Fig. Figure 1 shows a block diagram of a system for the fabrication of ε-phase MnAl / Co double-layer thin films according to an embodiment of the present disclosure; Fig. Figure 2 shows a schematic diagram illustrating the following: DC / RF magnetron sputtering system for thin-film deposition according to an embodiment of the present disclosure; Fig. Figure 3 shows a schematic diagram of the MnAl / Co (x = 1, 2, 3, 4, 5 nm) double-layer stack films deposited by sputtering according to an embodiment of the present disclosure; and Fig. Figure 4 shows a representative example. Room temperature X-ray diffraction pattern (XRD) of MnAl / Co (x = 1, 2, 3, 4, 5 nm) bilayer thin films according to an embodiment of the present disclosure.

[0017] Furthermore, those skilled in the art will recognize that the elements in the drawings are simplified and not necessarily drawn to scale. For example, the flowcharts illustrate the process by highlighting the main steps to facilitate understanding of this disclosure. With regard to the construction of the device, one or more components may be represented in the drawings by conventional symbols. The drawings may show only those specific details relevant to understanding the embodiments of this disclosure, so as not to clutter the drawings with details that are already apparent to those skilled in the art from the description contained herein. DETAILED DESCRIPTION:

[0018] To facilitate understanding of the principles of the invention, reference is made below to the embodiment illustrated in the drawings, which is described using specific terms. It is understood, however, that this does not limit the scope of protection of the invention. Rather, modifications and further developments of the illustrated system, as well as further applications of the inventive principles depicted therein, are conceivable, insofar as they would typically occur to a person skilled in the art in the field of the invention.

[0019] It will be clear to those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not to be understood as a limitation thereof.

[0020] References to “an aspect”, “another aspect”, or similar phrases in this description mean that a particular feature, structure, or property described in connection with the embodiment is included in at least one embodiment of the present disclosure. Therefore, phrases such as “in one embodiment”, “in another embodiment”, and similar expressions in this description may, but do not necessarily, all refer to the same embodiment.

[0021] The terms "includes," "comprehensive," or similar expressions denote non-exclusive inclusion. Thus, a procedure or method containing a list of steps does not only include those steps but may also include further steps not explicitly listed or inherent in the procedure or method. Likewise, the statement "includes..." for one or more devices, subsystems, elements, structures, or components, without further limitations, does not preclude the existence of other devices, subsystems, elements, structures, or components.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meanings generally known to those skilled in the art in the field to which this invention belongs. The systems, methods, and examples described herein serve only for illustration and are not to be understood as limiting.

[0023] Embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0024] Fig. Figure 1 shows a block diagram of a system for the fabrication of ε-phase MnAl / Co double-layer thin films according to an embodiment of the present disclosure.

[0025] according to Fig. 1 comprises: a) a high-frequency magnetron sputtering system (102) for depositing multilayer thin films on a silicon substrate, wherein the sputtering system (102) comprises: a base pressure maintenance system (102a) for maintaining a pressure of 3.99 × 10 -6kPa, three 2-inch targets made of MnAl, Co and Ta, and a substrate rotation mechanism (102b) for rotating the substrate at 30 revolutions per minute; b) a layer deposition unit (104) operationally connected to the RF magnetron sputtering unit (102), enabling the sputtering unit (102) to sequentially deposit: a 3 nm thick Ta buffer layer on the silicon substrate, a 60 nm thick MnAl layer on the Ta buffer layer, a Co layer with a thickness of 1 nm to 5 nm on the MnAl layer, and a 5 nm thick Ta top layer on the Co layer; c) an annealing unit (106) configured to anneal the deposited Ta and MnAl layers at 600 °C for 2 hours prior to depositing the Co layer;and d) a characterization unit (108) for analyzing the produced thin films, wherein the characterization unit (108) comprises: an X-ray diffraction system (XRD) for structural characterization, a 3D optical profilometer for measuring surface topography and mean roughness, and a field emission scanning electron microscope (FESEM) with energy-dispersive X-ray spectrometer (EDS) for analyzing surface morphology and elemental composition.

[0026] In one embodiment, the layer deposition unit (104) configures the sputtering unit (102) such that MnAl is deposited at a deposition rate of about 0.25 nm / min, Co at a deposition rate of about 0.16 nm / min and Ta at a deposition rate of about 1 nm / min.

[0027] In one embodiment, the thickness of the Co layer is adjusted between 1 nm and 5 nm to enable tunable magnetic behavior for the production of multiple thin films. The Co layer is configured to increase the saturation magnetization and coercive field strength through exchange coupling with the MnAl layer.

[0028] In one embodiment, the Ta top layer is configured to provide protection against oxidation and thus preserve the magnetic properties.

[0029] In one embodiment, the layer deposition unit (104) is configured such that the Co layer is deposited after annealing the Ta and MnAl layers at room temperature.

[0030] In one embodiment, the system (100) is configured to produce thin layers on substrates with dimensions of 1 cm × 1 cm.

[0031] In one embodiment, the layer deposition unit (104) is configured such that the layer thickness can be controlled by varying the power and the sputtering time.

[0032] In one embodiment, the manufactured two-layer thin films are configured for applications selected from the group consisting of spintronics applications, magnetic storage components and rare earth-free permanent magnets.

[0033] In one embodiment, the X-ray diffraction system of the characterization unit (108) comprises a Cu-Kα radiation source with a wavelength of 1.5406 Å and operates at a power of 3 kW.

[0034] The present invention relates to a system for the fabrication of ε-phase MnAl / Co bilayer thin films with enhanced magnetic properties. The system comprises an RF magnetron sputtering unit for the deposition of multilayer structures of Ta (3 nm) / MnAl (60 nm) / Co (x nm) / Ta (5 nm), where x varies from 1 to 5 nm, on silicon substrates. The system includes a deposition unit that sequentially deposits a Ta buffer layer, an MnAl layer, an ultrathin Co layer, and a Ta top layer. An annealing unit is used to anneal the Ta and MnAl layers at 600 °C for 2 hours before the Co deposition takes place at room temperature. The invention is characterized by an ultrathin Co layer that significantly increases the saturation magnetization and coercive field strength through exchange coupling with MnAl. The Ta top layer provides oxidation protection for long-term stability.The system enables adjustable magnetic behavior through the adaptation of the cobalt layer thickness and is therefore suitable for spintronic applications, magnetic storage devices, and rare-earth-free permanent magnets. A characterization unit consisting of XRD, a 3D optical profilometer, and FESEM with EDS allows for a comprehensive analysis of the structural, topographic, and chemical properties of the fabricated thin films.

[0035] As in Fig. As shown in Figure 2, thin films of Ta (3 nm) / MnAl (60 nm) / Co were produced by high-frequency magnetron sputtering. (x nm) / Ta (5 nm) (where x = 1, 2, 3, 4, 5) were deposited on a silicon substrate, as shown in Figure 2. Fig. Figure 3 shows the thickness of the deposited thin films in nanometers, indicated by the values ​​in parentheses. The base pressure of the sputtering system during the deposition process was 3.99 × 10⁻⁶. -6kPa. All target sizes are 2 inches, and three targets are used: MnAl, Co, and Ta. The sample size for the thin film is 1 cm × 1 cm.

[0036] To fabricate the MnAl / Co bilayer thin film, a 3 nm thick Ta layer was first deposited onto the silicon substrate, followed by a 60 nm thick MnAl layer. After MnAl deposition, the sample was annealed at 600 °C for 2 hours. Subsequently, a thin Co layer was deposited onto the MnAl layer at room temperature. In five parallel experiments, the thickness of the Co layer was adjusted to 1, 2, 3, 4, and 5 nm. Finally, a 5 nm thick Ta layer was deposited onto each sample. The Ta layer acts as a barrier against environmental influences, especially oxygen, and is frequently used as a topcoat or buffer layer. Its high oxidation resistance prevents the oxidation of the underlying ferromagnetic layers, which is essential for maintaining their magnetic properties. The deposition rates of MnAl, Co, and Ta are approximately 0.25, 0.16, and 1 nm / min, respectively.To ensure uniform layer deposition, the substrate was rotated at 30 revolutions per minute (rpm). This was intended to promote the uniform deposition of the layers. The layer thickness was controlled by varying the power and the sputtering time.

[0037] All thin films of Ta (3 nm) / MnAl (60 nm) / Co (x nm) / Ta (5 nm) (where x = 1, 2, 3, 4, 5) were fabricated by DC / RF magnetron sputtering (manufacturer: Mansha Vacuum Private Limited, Bangalore, India). X-ray diffraction patterns (XRD) for structural characterization were recorded using a Rigaku diffractometer Ultima IV with a Cu-Kα radiation source (λ = 1.5406 Å) at 3 kW power. The surface structure and mean roughness of the fabricated thin films were measured using a 3D profilometer (model: 3D Profilm, USA). The surface morphology and elemental composition of the thin films were investigated using a field emission scanning electron microscope (FESEM, ZEISS Sigma 300) with an energy-dispersive X-ray spectrometer (EDS, ZEISS Sigma).

[0038] The results demonstrated the cost-effective synthesis of MnAl / Co thin films on Si substrates via RF magnetron sputtering at room temperature. The crystal structure, surface topography, and atomic composition of the deposited thin films were investigated by X-ray diffraction (XRD), 3D profilometry, and energy-dispersive X-ray spectroscopy (EDS). The room-temperature XRD plots show that the fabricated layers crystallize in a hexagonal close-packed structure with a preferred (002) orientation. The XRD plots of the MnAl / Co thin films clearly show that the peak at 44.5° is due to the ultrathin Co layer. Fig.4) The 3D profilometry scans showed high homogeneity and low values ​​for the surface roughness parameters Sa and Ra of the deposited MnAl / Co layers. Sa represents the arithmetic mean, or mean absolute distance, between the surface points and the mean plane. Ra, on the other hand, is the arithmetic mean of the absolute ordinate values ​​Z(x) over the entire measurement period. A representative mapping of the surface roughness analysis of MnAl and MnAl / Co thin films yielded values ​​of Sa = 1.99 nm and Ra = 1.44 nm, and Sa = 2.23 nm and Ra = 1.1 nm, respectively. The composition of all produced MnAl layers was analyzed by energy-dispersive X-ray spectroscopy (EDX). The elemental distribution in the sample is shown in the EDX color charts, which also confirm the homogeneity and uniformity of the sample. The atomic ratio of manganese to aluminum is 12:88.Magnetic measurements at room temperature showed that the MnAl / Co layers are soft magnetic and the saturation magnetization (M. s ) in the range of 293-375 K.

[0039] This invention facilitates the fabrication of the ε-phase of MnAl / Co bilayer thin films. The tunable soft magnetic properties of the MnAl / Co thin films make them ideal for advanced electronic systems, energy-efficient actuators, and compact magnetic components used in industrial and consumer applications.

[0040] The drawings and the preceding description illustrate embodiments. Those skilled in the art will recognize that one or more of the described elements can be combined to form a single functional element. Alternatively, certain elements can be divided into several functional elements. Elements of one embodiment can be added to another. For example, the process flows described here can be modified and are not limited to the manner described herein. Furthermore, the actions of a flowchart need not be performed in the sequence shown; nor do all actions necessarily need to be carried out. Actions that do not depend on other actions can be performed in parallel with the other actions. The scope of protection of the embodiments is in no way limited by these specific examples. Numerous variations, whether explicitly stated in the description or not, such as...Differences in structure, dimensions, and materials are possible. The scope of protection of the embodiments is at least as comprehensive as described by the following claims.

[0041] The advantages, other benefits, and problem solutions have been described above with reference to specific embodiments. However, the advantages, benefits, problem solutions, and any components that can effect or enhance an advantage, benefit, or solution are not to be construed as critical, necessary, or essential features or components of the claims. REFERENCES 100 A system for the production of ε-phase MnAl / Co bilayer thin films. 102 High-frequency magnetron sputtering system 102a Base pressure maintenance system 102c substrate rotation mechanism 104 Layer Deposition Unit 106 annealing unit 108 Characterization Unit 202 DC / RF Generator 204 Si substrate 206 Target material (MnAl, Co and Ta)

Claims

[1] A system for the fabrication of ε-phase MnAl / Co double-layer thin films, consisting of: a) a high-frequency magnetron sputtering system for the deposition of multilayer thin films on a silicon substrate, the sputtering system comprising: • a system for maintaining base pressure, configured to maintain a constant pressure; • three 2-inch targets consisting of MnAl, Co and Ta; and • a substrate rotation mechanism configured to rotate the substrate at a constant number of revolutions per minute; b) a layer deposition unit that is operationally connected to the RF magnetron sputtering system and enables the sputtering system to deposit layers sequentially: • a 3 nm thick Ta buffer layer on the silicon substrate; • a 60 nm thick MnAl layer on the Ta buffer layer; • a Co layer with a thickness of 1 nm to 5 nm on the MnAl layer; and • a 5 nm thick Ta top layer on the Co layer; c) an annealing furnace configured to anneal the deposited Ta and MnAl layers for 2 hours at 600 °C before the Co layer is deposited; and d) a characterization unit for analyzing the produced thin films, wherein the characterization unit comprises the following: • an X-ray diffraction (XRD) system for structural characterization; • an optical 3D profilometer for measuring surface structure and mean roughness; and • a field emission scanning electron microscope (FESEM) with energy-dispersive X-ray spectrometer (EDS) for analyzing surface morphology and elemental composition. [2] System according to claim 1, wherein the layer deposition unit configures the sputtering unit such that MnAl is deposited at a deposition rate of about 0.25 nm / min, Co at a deposition rate of about 0.16 nm / min and Ta at a deposition rate of about 1 nm / min. [3] System according to claim 1, wherein for the production of multiple thin layers the thickness of the Co layer is adjusted between 1 nm and 5 nm to enable tunable magnetic behavior, wherein the Co layer is configured to increase the saturation magnetization and the coercive field strength by exchange coupling with the MnAl layer. [4] System according to claim 1, wherein the Ta cover layer is configured to provide protection against oxidation and thus maintain the magnetic properties. [5] System according to claim 1, wherein the layer deposition unit is configured such that the Co layer is deposited after annealing the Ta and MnAl layers at room temperature. [6] System according to claim 1, wherein the system is configured to produce thin layers on substrates with dimensions of 1 cm x 1 cm. [7] System according to claim 1, wherein the layer deposition unit is configured such that the layer thickness can be controlled by varying the power and the sputtering time. [8] System according to claim 1, wherein the produced two-layer thin films are configured for applications selected from the group consisting of spintronics applications, magnetic storage components and rare earth-free permanent magnets. [9] System according to claim 1, wherein the X-ray diffraction system of the characterization unit comprises a Cu-Kα radiation source with a wavelength of 1.5406 Å and operates at a power of 3 kW.

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