Inhomogeneous transition from the ferromagnetic state to the antiferromagnetic state in Mn₅(Ge_1-xSi_x)₃alloys: an NMR study

Hyperfine fields and anisotropy of the orbital moment in epitaxial Mn5Ge3 films studied by Mn55 NMR

“…The large frequency gap between the two spectrum components is due to a significant difference between the Mn magnetic moments in the two sites: 1.94μ B at the 4d site and 3.34μ B at the 6g site [9]. The observed NMR spectrum corresponds closely to the zero-field 55 Mn NMR spectrum previously reported in polycrystalline samples of this material [11]. However, further experiments carried out in presence of external magnetic field, as described in the following paragraphs, indicate the need to revisit some aspects of the interpretation given in Ref.…”

“…However, further experiments carried out in presence of external magnetic field, as described in the following paragraphs, indicate the need to revisit some aspects of the interpretation given in Ref. [11]. Figure 4 presents the NMR spectra recorded at a given (arbitrary) amplitude of the rf field for different values of the external dc magnetic field applied in the out-of-plane direction, i.e., along the crystallographic c axis.…”

“…However, these previous studies have been carried out on the randomly oriented polycrystalline samples and do not help to understand the anisotropic properties. Besides, due to the reported unusual behavior of NMR lines from two Mn crystal sites in presence of magnetic field [11], their shift in opposite directions calls for a closer look at this observation. (red), and Ge (blue).…”

“…We have used 55 Mn nuclear magnetic resonance (NMR), a powerful local tool giving selective information on manganese ions occupying two crystallographic sites and carrying distinctly different magnetic moments [9]. 55 Mn NMR studies in this compound have been previously reported in zero field [10] and in presence of the weak magnetic field (below magnetic saturation) [11]. However, these previous studies have been carried out on the randomly oriented polycrystalline samples and do not help to understand the anisotropic properties.…”

Simulation of the enhanced Curie temperature in Mn5Ge3Cx compounds

“…The first nearest neighbor Mn I -Mn I interactions J 1 ͑at the shortest distance of 2.526 Å͒ are ferromagnetic ͑FM͒ and clearly dominate over the corresponding Mn I -Mn II and Mn II -Mn II interactions, confirming the assumption about the different magnitude of exchange interaction for Mn atoms in different sublattices. 14 The dependence of the exchange parameters on the interatomic distances is stronger for the Mn II sublattice, while it is weaker for the Mn I one. As it follows from Table II, in Mn 5 Ge 3 there is an AFM J 3 interaction between the Mn II atoms within z = 1 4 and z = 3 4 planes ͑perpendicular to the c-axis͒, and FM J 4 and J 6 interactions between Mn II belonging to different planes.…”