Evidence of a perpendicular magnetocrystalline anisotropy in aMn5Ge3epitaxial thin film revealed by ferromagnetic resonance

Abstract

A systematic study of the angular and temperature dependencies of the ferromagnetic resonance (FMR) of manganese germanide Mn 5 Ge 3 grown on Ge(111) by solid phase epitaxy is reported. The FMR measurements performed in the out-of-plane geometry show that an out-of-plane anisotropy contribution exists in this material, and it increases with decreasing temperatures. However, the perpendicular magnetization curves imply that the shape anisotropy determines the orientation of the magnetization at any temperature. It is also shown that the Callen-Callen law cannot be used to describe the temperature dependence of the perpendicular anisotropy in Mn 5 Ge 3. Such temperature dependence of the magnetocrystalline anisotropy shows the invalidity of the single-ion anisotropy model for Mn 5 Ge 3 .

Ferromagnetic resonance in Mn5Ge3 epitaxial films with weak stripe domain structure

“…A similar broad absorption signal was observed at low fields in the FMR experiments on thin films of Heusler alloy Co 2 MnGa with stripe domain structure [12]. It is interesting to note that this signal has not been reported in previous FMR studies on Mn 5 Ge 3 thin films [8,28], even though they present FMR results in the unsaturated state.…”

“…This conclusion negates the interpretation of FMR data in Mn 5 Ge 3 films presented in Ref. [8], where the authors claim that magnetization is entirely oriented in the film plane, and interpret the acoustic resonance mode as the uniform FMR mode. Our results stress the importance of combining the analysis of the FMR modes observed in magnetically non saturated materials with micromagnetic calculations and simulations of a domain structure.…”

“…Meanwhile, another study in Mn 5 Ge 3 films prepared with the same technique [8], has reported-based on the analysis of Ferromagnetic Resonance (FMR) experiments-that in spite of the demonstrated uniaxial anisotropy perpendicular to the film plane, magnetization is oriented in sample plane, within the investi-gated range of temperatures (30-290 K), even in samples as thick as 30 nm. This evident discrepancy requires a closer examination, especially since the FMR experiments reported in [8] were performed at 9.08 GHz (Xband), and the corresponding FMR signals were observed at magnetic field values below sample saturation, therefore some kind of domain structure can be expected. To resolve these discrepancies and to get a deeper insight into the magnetic properties of epitaxial thin films prepared by SPE method, we have undertaken an extensive FMR study in the Q-band, where the FMR resonance takes place in a fully saturated sample, as well as in the X-band (in presence of a domain structure).…”

Ferromagnetic resonance and magnetic damping in C-doped Mn5Ge3

“…The positive sign of K 2 indicates that this term favors an out-of-plane easy axis of magnetisation while the shape anisotropy dominates [25]. In the very thin film limit, K 2 could overcome the shape anisotropy resulting in an out-of-plane anisotropy axis.…”

Role of nitrogen on the magnetic properties of MBE grown Mn0.04Ge0.96 films

“…This signal can be attributed to ferromagnetic Mn 5 Ge 3 clusters since the Curie temperature of Mn 5 Ge 3 is 296 K, as reported in the literature [27,28]. However, the resonance field only slightly depends on the direction of the external magnetic field relative to the crystallographic c axis of the sample, unlike Mn 5 Ge 3 thin films which show a strong perpendicular magnetic anisotropy [29]. Since shape anisotropy determines the orientation of the magnetization, precipitation of nanometer sized Mn 5 Ge 3 occurs with nitrogen incorporation.…”