The multilayer of approximate structure MgO(100)/[ n fe 51 Rh 49 (63 Å)/ 57 fe 51 Rh 49 (46 Å)] 10 deposited at 200 °C is primarily of paramagnetic A1 phase and is fully converted to the magnetic B2 phase by annealing at 300 °C for 60 min. Subsequent irradiation by 120 keV Ne + ions turns the thin film completely to the paramagnetic A1 phase. Repeated annealing at 300 °C for 60 min results in 100% magnetic B2 phase, i.e. a process that appears to be reversible at least twice. The A1 → B2 transformation takes place without any plane-perpendicular diffusion while Ne + irradiation results in significant interlayer mixing. Besides the traditional "faster-smaller-cheaper" directive, a new requirement has recently arisen for the newly developed devices: the energy efficiency. The electricity consumption of information technology is expected to reach 13% of the global utilization in the next decade 1,2 , of which nearly 50% is due to unwanted heat dissipation. Therefore, the study of novel materials and developing new operation principles for energy-saving applications in information technology are essential for supporting sustainable development. From this point of view, the fine control of magnetism is a great step towards reducing energy consumption of information storage by orders of magnitude 3-11. The Fe-Rh system is an excellent playground for developing energy-efficient magnetic devices 12,13. The equilibrium phase diagram of solid Fe-Rh 14,15 includes a great variety of phases of different magnetic behaviour. The disordered bcc A2 (α or δ, prototype W) phases are, depending on temperature, ferro-or paramagnetic (PM). The ordered bcc B2 (α' or α'' , prototype CsCl) phases show ferro-, antiferro-or paramagnetism at different temperatures and concentrations. The disordered fcc A1 (γ, prototype Cu) phase is PM at all investigated temperatures. The existence of a monoclinic antiferromagnetic (AFM) ground state was predicted by DFT calculations in the equiatomic FeRh alloy in 2016 16. However, this phase could not be identified in thin films by Wolloch and co-workers 17. Using nuclear resonant inelastic X-ray scattering (NRIXS), these latter authors analysed the lattice dynamical contribution to the phase stability in FeRh and demonstrated that the AFM ground state was stabilized by phonon softening. With increasing temperature, the nearly equiatomic FeRh alloy of B2 structure undergoes a metamagnetic transition from the low-temperature AFM α'' to the high-temperature ferromagnetic (FM) α' phase close to room temperature (RT) 18-27. In the AFM phase, Fe atoms carry a magnetic moment of 3.3 μ B of alternating direction while the Rh atoms possess inconsiderable magnetic moment 22. Conversely, in the FM phase, Fe and Rh atoms carry parallel moments of 3.2 μ B and 0.9 μ B , respectively 28-30. This magnetic transition is accompanied with a reduction of the resistivity and an ~ 0.6% isotropic strain of the crystal lattice 21,31. By introducing strain in the FeRh crystal lattice, this phenomenon can be reversed and the mag...

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Magnetic nanopatterns were successfully created in FeRh thin film deposited on MgO (100) substrates. Silica and polystyrene spherical masks, nominally 500 and 1000 nm in diameter, respectively were applied on the surface of the sample in order to locally shadow the film against the effect of 110 keV energy neon-ion irradiation with fluences of 1015 and 1016 ions/cm2. Such nanosphere-lithography technique allows for projecting the mask geometry on the magnetic structure of the FeRh film. Conversion-electron Mössbauer spectroscopy and magnetic force microscopy were used to determine the ferromagnetic ratio and the magnetic pattern in the samples, and nuclear resonance scattering of synchrotron radiation was applied to obtain the in-depth magnetic profile. From the results obtained, the possible three-dimensional (3D) structure of the created individual magnetic domains was also constructed. Overall, the great customizability of the presented nanosphere-lithography technique in FeRh thin film provides opportunities for developing cutting-edge spintronic applications.