Mn 3 Ga , a compensated ferrimagnet with high Curie temperature and low magnetic moment for spin torque transfer applications

Abstract

This work reports about the electronic, magnetic, and structural properties of the binary compound Mn3Ga. The tetragonal DO22 phase of Mn3Ga was successfully synthesized and investigated. It has been found that the material is hard magnetic with an energy product of Hc×Br=52.5kJm−3 and an average saturation magnetization of about 0.25μB∕at. at 5K. The saturation magnetization indicates a ferrimagnetic order with partially compensating moments at the Mn atoms on crystallographically different sites. The Curie temperature is above 730K where the onset of decomposition is observed. The electronic structure calculations indicate a nearly half-metallic ferrimagnetic order with 88% spin polarization at the Fermi energy.

Basics and prospective of magnetic Heusler compounds

“…The martensitic to austenitic phase transition in shape memory alloys and magneto-caloric Heusler compounds is phase transitions from an anisotropic (tetragonal, orthorhombic, or complex modulated structures) to an isotropic cubic structure. 39 Mn 3 Ga and Mn 3−x Ga possess the stable tetragonal structure at ambient conditions, 31,40,41 as well as the perpendicular magnetization of their thin film electrodes, which suggests them as potential candidate materials for the STT RAM devices. [42][43][44] In general, Heusler compounds with low saturation magnetic moment, high magnetic crystalline anisotropy, low Gilbert damping, but high spin-polarization and high Curie temperature, are required to minimize the switching current and increase the switching speed in STT-MRAM devices according to the Slonczewski-Berger equation.…”

“…28 One of the few examples of a half metallic Mn 2 -Heusler compound with ferromagnetic coupling between the two manganese atoms is Mn 2 VAl, 29 with less than 24 VEC (see Figure 3(c)). Most of the Mn 2 YZ compounds are very different from Co 2 YZ and Mn 2 VAl and crystallize in the inverse Heusler structure, 4 where the manganese moments sitting on two different sites are coupled parallel to one another 30,31 (each Mn sits on a crystallographically distinguishable site, as illustrated in Figure 4). Cubic Mn 3 Ga with 24 valence electrons is a "borderline compound" and is a fully compensated ferrimagnet [30][31][32] principally different from non-magnetic semiconductors like Fe 2 VAl due to the special role of manganese in Heusler compounds.…”

“…Most of the Mn 2 YZ compounds are very different from Co 2 YZ and Mn 2 VAl and crystallize in the inverse Heusler structure, 4 where the manganese moments sitting on two different sites are coupled parallel to one another 30,31 (each Mn sits on a crystallographically distinguishable site, as illustrated in Figure 4). Cubic Mn 3 Ga with 24 valence electrons is a "borderline compound" and is a fully compensated ferrimagnet [30][31][32] principally different from non-magnetic semiconductors like Fe 2 VAl due to the special role of manganese in Heusler compounds. 12,30 The magnetic moments on the different sites have different magnetization directions, which lead to a complete compensation of the magnetic moments, see Figure 4(a).…”

Site-specific order and magnetism in tetragonal Mn3Ga thin films

“…While the cubic L2 1 Heusler alloys are virtually isotropic, their tetragonal cousins can display very high uniaxial magnetic anisotropy coupled with tunable saturation magnetization and high spin polarization. This is especially true in the case of D0 22 Mn 3 Ga. [15][16][17][18] Thin films of this material exhibit high, perpendicular, uniaxial anisotropy and grow with ease on both MgO and SrTiO 3 substrates, as well as a number of lattice matched seed layers like Cr and Pt.…”

Structural, magnetic, and electron transport properties of Mn3−xPtxSn (x = 0, 0.5, 1) nanomaterials

“…4 It has been found recently that the Mn-based tetragonal compound Mn 3Àx Ga (x ¼ 2-3) is a promising materials for STT applications. 5,6 However, its large lattice mismatch with MgO and relatively high magnetization are drawbacks. Another Mn-based compound predicted to have high potential for STT application is tetragonal Mn 3Àx Y x Sn (Y ¼ 4d or 5d elements).…”