Reconstruction control of magnetic properties during epitaxial growth of ferromagnetic Mn3-deltaGa on Wurtzite GaN(0001)

MnGa-based fully perpendicular magnetic tunnel junctions with ultrathin Co2MnSi interlayers

Because tetragonal structured MnGa alloy has intrinsic (not interface induced) giant perpendicular magnetic anisotropy (PMA), ultra-low damping constant and high spin polarization, it is predicted to be a kind of suitable magnetic electrode candidate in the perpendicular magnetic tunnel junction (p-MTJ) for high density spin transfer torque magnetic random access memory (STT-MRAM) applications. However, p-MTJs with both bottom and top MnGa electrodes have not been achieved yet, since high quality perpendicular magnetic MnGa films can hardly be obtained on the MgO barrier due to large lattice mismatch and surface energy difference between them. Here, a MnGa-based fully p-MTJ with the structure of MnGa/Co₂MnSi/MgO/Co₂MnSi/MnGa is investigated. As a result, the multilayer is with high crystalline quality, and both the top and bottom MnGa electrodes show well PMA. Meanwhile, a distinct tunneling magnetoresistance (TMR) ratio of 65% at 10 K is achieved. Ultrathin Co₂MnSi films are used to optimize the interface quality between MnGa and MgO barrier. A strong antiferromagnetic coupling in MnGa/Co₂MnSi bilayer is confirmed with the interfacial exchange coupling constant of −5erg/cm². This work proposes a novel p-MTJ structure for the future STT-MRAM progress.

Artificially engineered Heusler ferrimagnetic superlattice exhibiting perpendicular magnetic anisotropy

To extend density limits in magnetic recording industry, two separate strategies were developed to build the storage bit in last decade, introduction of perpendicular magnetic anisotropy (PMA) and adoption of ferrimagnetism/antiferromagnetism. Meanwhile, these properties significantly improve device performance, such as reducing spin-transfer torque energy consumption and decreasing signal-amplitude-loss. However, materials combining PMA and antiferromagnetism rather than transition-metal/rare-earth system were rarely developed. Here, we develop a new type of ferrimagnetic superlattice exhibiting PMA based on abundant Heusler alloy families. The superlattice is formed by [MnGa/Co₂FeAl] unit with their magnetizations antiparallel aligned. The effective anisotropy (K_u^eff) over 6 Merg/cm³ is obtained, and the SL can be easily built on various substrates with flexible lattice constants. The coercive force, saturation magnetization and K_u^eff of SLs are highly controllable by varying the thickness of MnGa and Co₂FeAl layers. The SLs will supply a new choice for magnetic recording and spintronics memory application such as magnetic random access memory.

Multifunctional L1(0) -Mn(1.5)Ga films with ultrahigh coercivity, giant perpendicular magnetocrystalline anisotropy and large magnetic energy product

A new kind of multifunctional L1(0) -Mn(1.5)Ga film is demonstrated for the first time. These MBE-grown epitaxial films exhibit pronounced magnetic properties at room temperature, including ultrahigh perpendicular coercivity up to 42.8 kOe, giant perpendicular magnetic anisotropy with a maximum of 21.7 Merg/cm(3) and large magnetic energy products up to 2.60 MGOe, which allow various applications in ultrahigh density recording, spintronics, and permanent magnets.