Ferromagnetic resonance, transverse bias initial inverse susceptibility and torque studies of magnetic properties of Co2MnSi thin films

M Belmeguenai,Y Roussigné,K Westerholt,H Tuzcuoglu,T Devolder,S.M Chérif,D Berling,P Tiberto,F Pratt,F Casoli,M Affronte,P Vavassori,M Solzi,C Marquina,C De Julián Fernández,S Tacchi,G Gubbiotti

doi:10.1051/epjconf/20134018001

Abstract

Magnetic properties of Co2MnSi thin films of 20 nm and 50 nm in thickness grown by radio frequency sputtering on a-plane sapphire substrates have been studied. X-ray diffraction (XRD) revealed that the cubic Co2MnSi axis is normal to the substrate and that well defined preferential in-plane orientations are present. The static magnetic properties were studied at room temperature by conventional magneto-optical Kerr effect (MOKE), transverse bias initial inverse susceptibility and torque (TBIIST) MOKE. The dynamic magnetic properties were investigated by micro-strip ferromagnetic resonance (MS-FMR) at room temperature. The resonance and TBIIST measurements versus the direction of the in-plane applied magnetic field reveal that the in-plane anisotropy results from the superposition of a two-fold and a four-fold symmetry. The directions of the principal axes of the twofold anisotropy are sample dependent. The angular dependence of remanent normalized magnetizations and coercive fields, studied by MOKE are analyzed within the frame of a coherent rotation model. A good agreement is observed between the field anisotropy values obtained from MS- FMR and from TBIIST data. Frequency and angular dependence of FMR linewidth has been studied. Apparent damping coefficient of 0.0112 has been measured for 50 nm thick sample.

Highlights

Cobalt-based full-Heusler with a general composition Co2YZ (Y is element of the transition metal group, whereas the Z component comes from the group III-V elements) alloys are the most interesting class of Heusler materials for spintronic applications due to their predicted 100% spin-polarization and their high Curie temperature largely exceeding the room temperature
Co2MnSi full Heusler, which has a Curie temperature of 985K, is one of the most studied full-Heusler alloys. It has been used in magnetic tunnel junctions with different barriers [2,3,4] where very high tunnelling magnetoresistance (TMR) ratios are obtained. Recently, it was reported the enhancement of the resistance change area product and large magnetoresistance ratio in current perpendicularto-plane giant magnetoresistance (CPP GMR) in epitaxially grown Co2MnSi based trilayers
Field-dependences of the resonance frequencies of the uniform and of the perpendicular standing spin wave (PSSW: detectable only for 50 nm thick film) modes are shown on figure 3 for both samples

Summary

Introduction

Cobalt-based full-Heusler with a general composition Co2YZ (Y is element of the transition metal group, whereas the Z component comes from the group III-V elements) alloys are the most interesting class of Heusler materials for spintronic applications due to their predicted 100% spin-polarization and their high Curie temperature largely exceeding the room temperature. Co2MnSi full Heusler, which has a Curie temperature of 985K, is one of the most studied full-Heusler alloys It has been used in magnetic tunnel junctions with different barriers [2,3,4] where very high TMR ratios are obtained. Recently, it was reported the enhancement of the resistance change area product and large magnetoresistance ratio in current perpendicularto-plane giant magnetoresistance (CPP GMR) in epitaxially grown Co2MnSi based trilayers. EPJ Web of Conferences particular provides an accurate value of the anisotropy field strength in the sample and a precise determination of the anisotropy axes

Sample and experimental set up

Static properties

Dynamic properties