Evolution of ferromagnetic and spin-wave resonances with crystalline order in thin films of full-Heusler alloy Co2MnSi

TL;DR

This study investigates how crystalline order affects magnetic properties and spin-wave resonances in Co2MnSi thin films, revealing increased order enhances magnetic moments and anisotropy, with detailed analysis of exchange interactions.

Contribution

It provides a comprehensive analysis of magnetic anisotropy and exchange stiffness in Co2MnSi films as a function of crystalline order and temperature, combining experimental and ab-initio methods.

Findings

Maximum magnetic moment of 4.95 μB per formula unit at 600°C annealing

Exchange stiffness constant evaluated down to 100 K

Crystalline order correlates with magnetic anisotropy and exchange energies

Abstract

We report the evolution of magnetic moment as well as magnetic anisotropy with crystalline order in Co$_2$MnSi thin films grown on $(100)$ MgO by pulsed laser deposition. The films become more ordered as the annealing temperature ($T_A$) increases from 400 to 600 $^0$C. The extent of \emph{L}$2_1$ ordering in the films annealed at 600 $^0$C is $\approx 96%$. The static magnetization measurements by vibrating sample magnetometry shows a maximum moment of 4.95 $\mu_B$ per formula unit with low coercivity ($H_C$ $\approx$ 65 Oe) in the films annealed at 600 $^0$C. A rigorous analysis of the azimuthal and polar angle dependent ferromagnetic resonance (FMR) measured at several temperatures allows determination of various anisotropy fields relevant to our system as a function of $T_A$. Finally, we have evaluated the exchange stiffness constant down to 100 K using spin wave modes in FMR spectra. We have also estimated the exchange energies as well as stiffness constant by varying the lattice parameter \emph{ab-initio} using the Korringa-Kohn-Rostoker method.