Paramagnetic to antiferromagnetic phase transformation in sputter deposited Pt–Mn thin films

Abstract

Sputter deposited, equiatomic Pt-Mn thin films used in giant magnetoresistive spin valves are found not to exist in the antiferromagnetic state required for device operation. Therefore, an annealing step is needed to induce a phase transformation from the as-deposited, paramagnetic A1 ͑fcc͒ phase to the antiferromagnetic L1 0 phase. The L1 0 phase is the thermodynamically stable configuration, but favorable kinetics for the transformation were only found above 260°C. The A1 to L1 0 phase transformation was studied by x-ray diffraction, transmission electron microscopy and differential scanning calorimetry ͑DSC͒. The nucleation and growth conditions were evaluated and an exothermic transformation enthalpy of Ϫ12.1 kJ/mol of atoms was determined. The kinetics of the reaction were simulated using the Johnson-Mehl-Avrami analysis, where the necessary parameters were determined by the Kissinger and Ozawa methods from constant scanning rate DSC experiments ͓H. Yinnon and D. R. Uhlmann, J. Non-Cryst. Solids 54, 253 ͑1983͔͒. The resulting simulations were compared to DSC data as well as isothermal x-ray peak shift data and a reasonable agreement was obtained.

Spin-orbit torque switching of an antiferromagnetic metallic heterostructure

“…After fabrication, we anneal the structures at 300 °C for 2 h. Out-of-plane x-ray diffraction (XRD) spectra indicate a textured polycrystalline orientation along the (111) direction (see supplementary Fig. S1 ), consistent with previous reports 31 , 33 . We obtain an average grain size of 10 ± 2 nm by using Scherrer’s formula.…”

Cs2NaGaBr6: a new lead-free and direct band gap halide double perovskite

“…For dynamical stability C 0 > 0. 44 The positive value of C 0 for the materials under investigation (Table 2) predicted that these materials are mechanically stable.…”

Paramagnetic-to-antiferromagnetic phase transformation in sputter-deposited Ni-Mn thin films

“…Detailed information about transformation kinetics can be obtained from DSC results on multilayered thin films. 12,13 However, caution must be used in directly associating the results of this study with GMR devices. To best compare the enthalpy of transformation data with calculated values, we chose to use freestanding single-layer films.…”