Magnetostrictronics: an example case of bulk L10-MnPt from first-principles calculations

Abstract

Sustainable development beyond ferromagnetic (FM) or anti-ferromagnetic (AFM) spintronics using rear-earth (RE)-free hard magnetic materials is novel and under-explored. One possible route would be utilizing the internal energies of hard magnets by convolution of elastic and magnetic anisotropic energies to work done, which is the main scope of the current proposal. This essentially is viable by exploring and better understanding the elastic tensor stiffness coefficients and the magneto-crystalline energy calculation of the magnet at the correct magnetic ground state or, say, correct anisotropic spin-axis choice. Magneto-crystalline anisotropic energy (MCAE) from alignment of spins is thus crucial to manipulate the device transport character while magnetized, which are, however, strongly bound to the crystal orbitals. A measure of MCAE through spin–orbital coupling (SOC) is intrinsic in the unstrained state of the magnets, while the associated stress–strains (via magneto-elastic constants) due to spin–orbital ordering and rearrangement can be used to reveal the domain – magnetostrictronics – and this is investigated herein in bulk L1₀-MnPt. The observed in-plane MCAE is validated and the microscopic origin is explained from non-collinear spin-polarized total energy subtractions, and corroborated with the calculated anisotropic constants, K, from the tetragonality of the crystal, and finally, with the SOC matrices of those composing elements, Mn and Pt. These anisotropic energies are also decoupled from the convolution of the orbital contributions (eigenfunctions) into orbital energies (band energies) of these two Mn,Pt sublattices. From the observed Mn-p band energies, the MCAE cancellation from the d-bands of the 3d-metal is further anticipated and helps us further to reveal the microscopic origin of the lower value of MCAE in AFM ordering vs. the twice larger MCAE values in FM ordered prototype phase L1₀-FePt.