The more and more challenging requests of the data storage industry and new findings in the field of Spintronics have driven the interest of Magnetism research community towards the design and growth of thin films with high structural quality. Since the Nineties, several research groups have demonstrated the possibility to employ a sputtering apparatus to epitaxially grow thin films of metallic alloys with different functional magnetic properties, e.g. huge magnetocrystalline anisotropy, ferromagnetic shape-memory, giant magnetoresistance. This demonstration has paved the way to the development of new devices, leading in some cases to important technological breakthroughs, as in the case of hard disk's reading heads based on the tunnel magnetoresistance effect. We have used a RF sputtering apparatus to grow epitaxial thin films or heterostructures of different magnetic metallic materials [1-5], exploiting the alternate deposition from three targets to obtain specific and variable compositions of the alloys. Using single-crystalline substrates with different lattice parameters, i.e., MgO, SrTiO3, and LSAT, we have obtained epitaxial films (thickness from 10 to 200 nm) of two magnetic Heusler alloys: Ni-Mn-Ga and Mn-Ga. The films show a variety of different morphologies and microstructures, depending on substrate, film thickness and growth temperature [1-3]. Our studies demonstrate that controlling structure and microstructure is crucial for tailoring magnetism. We have achieved a giant and anisotropic magnetization jump by microstructure engineering in magnetic shape-memory Ni-Mn-Ga films, which have a great potential for the fabrication of new-concept actuators, sensors and energy harvesters [1]. We have also been able to epitaxially grow thin films of the metastable tetragonal phase of Mn-Ga (close to Mn3Ga composition) [3]; these films possess exceptional magnetic and electronic properties, which make them promising as ferromagnetic electrodes in Spin-Transfer-Torque Magnetic RAMs. For both these Heusler alloys we have realized nanodots by self-assembly nanolithography [4, figure 1]. Recent Publications 1.P. Ranzieri et al. (2015) Achieving Giant Magnetically Induced Reorientation of Martensitic Variants in Magnetic Shape-Memory Ni-Mn-Ga Films by Microstructure Engineering. Advanced Materials 27: 4760-4766. 2.P. Ranzieri et al. (2013) Epitaxial Ni-Mn-Ga/MgO(1 0 0) thin films ranging in thickness from 10 to 100 nm. Acta Materialia 61: 263-272. 3.J. Karel et al. (2016) Evidence for In-Plane Tetragonal c-axis in MnxGa1-x Thin Films using Transmission Electron Microscopy. Scripta Materialia 114: 165-169. 4.J. Karel et al. (2016) MnxGa1-x Nanodots with High Coercivity and Perpendicular Magnetic Anisotropy. Applied Surface Science 387: 1169-1173. 5.F. Casoli et al. (2016) Exchange-Coupled Composite Media, in "Ultra-High-Density Magnetic Recording: Storage Materials and Media Designs", pp 279-326, Pan Stanford Publishing, Editors: G. Varvaro, F. Casoli.
Heusler alloy thin films for data storage and energy
Francesca Casoli
2017
Abstract
The more and more challenging requests of the data storage industry and new findings in the field of Spintronics have driven the interest of Magnetism research community towards the design and growth of thin films with high structural quality. Since the Nineties, several research groups have demonstrated the possibility to employ a sputtering apparatus to epitaxially grow thin films of metallic alloys with different functional magnetic properties, e.g. huge magnetocrystalline anisotropy, ferromagnetic shape-memory, giant magnetoresistance. This demonstration has paved the way to the development of new devices, leading in some cases to important technological breakthroughs, as in the case of hard disk's reading heads based on the tunnel magnetoresistance effect. We have used a RF sputtering apparatus to grow epitaxial thin films or heterostructures of different magnetic metallic materials [1-5], exploiting the alternate deposition from three targets to obtain specific and variable compositions of the alloys. Using single-crystalline substrates with different lattice parameters, i.e., MgO, SrTiO3, and LSAT, we have obtained epitaxial films (thickness from 10 to 200 nm) of two magnetic Heusler alloys: Ni-Mn-Ga and Mn-Ga. The films show a variety of different morphologies and microstructures, depending on substrate, film thickness and growth temperature [1-3]. Our studies demonstrate that controlling structure and microstructure is crucial for tailoring magnetism. We have achieved a giant and anisotropic magnetization jump by microstructure engineering in magnetic shape-memory Ni-Mn-Ga films, which have a great potential for the fabrication of new-concept actuators, sensors and energy harvesters [1]. We have also been able to epitaxially grow thin films of the metastable tetragonal phase of Mn-Ga (close to Mn3Ga composition) [3]; these films possess exceptional magnetic and electronic properties, which make them promising as ferromagnetic electrodes in Spin-Transfer-Torque Magnetic RAMs. For both these Heusler alloys we have realized nanodots by self-assembly nanolithography [4, figure 1]. Recent Publications 1.P. Ranzieri et al. (2015) Achieving Giant Magnetically Induced Reorientation of Martensitic Variants in Magnetic Shape-Memory Ni-Mn-Ga Films by Microstructure Engineering. Advanced Materials 27: 4760-4766. 2.P. Ranzieri et al. (2013) Epitaxial Ni-Mn-Ga/MgO(1 0 0) thin films ranging in thickness from 10 to 100 nm. Acta Materialia 61: 263-272. 3.J. Karel et al. (2016) Evidence for In-Plane Tetragonal c-axis in MnxGa1-x Thin Films using Transmission Electron Microscopy. Scripta Materialia 114: 165-169. 4.J. Karel et al. (2016) MnxGa1-x Nanodots with High Coercivity and Perpendicular Magnetic Anisotropy. Applied Surface Science 387: 1169-1173. 5.F. Casoli et al. (2016) Exchange-Coupled Composite Media, in "Ultra-High-Density Magnetic Recording: Storage Materials and Media Designs", pp 279-326, Pan Stanford Publishing, Editors: G. Varvaro, F. Casoli.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
