Co2FeAl thin films grown on MgO substrates: Correlation between static, dynamic, and structural properties

Abstract

Co2FeAl (CFA) thin films with thickness varying from 10 nm to 115 nm have been deposited on MgO(001) substrates by magnetron sputtering and then capped by Ta or Cr layer. X-rays diffraction (XRD) revealed that the cubic [001] CFA axis is normal to the substrate and that all the CFA films exhibit full epitaxial growth. The chemical order varies from the B2 phase to the A2 phase when decreasing the thickness. Magneto-optical Kerr effect (MOKE) and vibrating sample magnetometer measurements show that, depending on the field orientation, one or two-step switchings occur. Moreover, the films present a quadratic MOKE signal increasing with the CFA thickness, due to the increasing chemical order. Ferromagnetic resonance, MOKE transverse bias initial inverse susceptibility and torque (TBIIST) measurements reveal that the in-plane anisotropy results from the superposition of a uniaxial and of a fourfold symmetry term. The fourfold anisotropy is in accord with the crystal structure of the samples and is correlated to the biaxial strain and to the chemical order present in the films. In addition, a large negative perpendicular uniaxial anisotropy is observed. Frequency and angular dependences of the FMR linewidth show two magnon scattering and mosaicity contributions, which depend on the CFA thickness. A Gilbert damping coefficient as low as 0.0011 is found. arXiv:1305.0714v1 [cond-mat.mtrl-sci]

Magnetic and structural properties of Co2FeAl thin films grown on Si substrate

“…1a). The lattice parameter (a), shown on Figure 1b, increases with the increasing CFA thickness, similarly to samples grown on MgO substrates where a direct correlation exists with the enhancement of the chemical order [9], however the lattice parameters remain smaller than the reported one in the bulk compound with the L2 1 structure (0.574 nm). Due to the overlap of the potential (002) CFA peak with the substrate reflections it is difficult to accurately evaluate de degree of chemical order in our films.…”

Effect of the annealing temperature on dynamic and structural properties of Co2FeAl thin films

“…After the growth of the stack, the structures were The structural properties of the samples have been characterized by X-ray diffraction (XRD) using a fourcircle diffractometer. Their magnetic static and dynamic properties have been studied by vibrating sample magnetometer (VSM) and microstrip ferromagnetic resonance (MS-FMR) [5], respectively.…”

“…All the measurements presented here have been made at room temperature and analysed using the model presented in [5].…”

Tunable magnetization relaxation of Fe2Cr1−xCoxSi half-metallic Heusler alloys by band structure engineering

“…Both properties are favorable for STT [9]. However, except for a few Co-based Heusler alloys, the damping constant is larger than for Fe films (0.002), probably due to band broadening by structural defects, chemical disorder and magnon excitation [13,[24][25][26][27][28]. Furthermore, Heusler alloys usually exhibit large anisotropy in the ferromagnetic resonance (FMR) linewidth [26,29], which may lead to large variation in performance among devices.…”