Anomalies in electron spin resonance spectra of Ge1−xMnxTe diluted magnetic semiconductors

Abstract

We report on magnetic properties and X-band electron spin resonance (ESR) study (80–430 K) of diluted magnetic semiconductors Ge1−xMnxTe (x=0.07–0.44) revealing ferromagnetism with the Curie temperature achieving 90 K. Effective magnetic moment peff per Mn2+ ion estimated from the Curie constant in the range 0.15≤x≤0.26 increases from 2.27 to 2.95 μB. The temperature evolution of ESR spectra was found to have a complicated character. We observed the presence of two distinct absorption lines of Dysonian type, associated with two resonance centers in these diluted magnetic semiconductors. Possible origin of these two lines has been analyzed and clustering effect was proposed to be most likely responsible for anomalous behavior. Anomalies in temperature dependencies of the linewidths and g-factors were observed at temperatures lower than 160 K. We connect these anomalies with magnetic fluctuations in the vicinity of transition to ferromagnetic phases. The anomalous broadening of the linewidth in paramagnetic region occurs with decreasing of the temperature similarly to ESR behavior of related A M2nB6 diluted magnetic semiconductors. This broadening is satisfactorily described in the framework of modified Huber’s theory. At the same time, the g-factor is essentially independent on both temperature and alloy composition. Average values of effective g-factor for two resolved spectral components at room temperature were found to be g1=2.02–2.07 and g2≈1.99.

Half-metallicity and magnetism of GeTe doped with transition metals V, Cr, and Mn: A theoretical study from the viewpoint of application in spintronics

“…1,18 Highest reported T c is around 130-140 K for Mn concentration x slightly over 50% in the Ge-Mn sublattice; and for x ¼ 0.25, T c is $70 K. 1 Other authors report T c values more or less in the same range depending on Mn concentration. 2,7,16 T c values reported for RS or nearly RS Ge 1Àx Cr x Te films are higher. 5 Note that the lattice parameters reported for x ¼ 0.24 and 0.55 in Ge 1Àx Mn x Te are 5.939 and 5.895 Å , respectively, which compare well with our calculated values 5.964 and 5.914 Å , for x ¼ 0.25 and 0.50, respectively (Table I).…”

“…Experimentally, Ge 1Àx Mn x Te alloys, with X ¼ Cr, Mn, Fe have been reported to exhibit ferromagnetic behavior [11][12][13][14][15][16][17][18][19][20][21] over wide range of the concentration x. The structure of these compounds, grown as thin films, is usually found to be RS or small deviations from this.…”

“…Recently, a large number of experimental studies related to magnetism and magnetic transitions in several Ge-Te based alloys, such as Ge-Cr-Te, Ge-Mn-Te, and Ge-Fe-Te) have been reported. [11][12][13][14][15][16][17][18][19][20][21] In addition, there is substantial amount work on DMSs in general (for a review see Ref. 22), where the magnetic properties arise via percolation effects among a very small concentration of the magnetic atoms.…”

Crucial Role of Site Disorder and Frustration in Unusual Magnetic Properties of Quasi-2D Triangular Lattice Antimonate Na4FeSbO6

“…In magnetic systems with low dimensionality, the rate at which the spin correlation decays as a function of time is reduced compared with 3D systems because of the limitation in the possible paths of diffusion [6]. Note that such sort of critical broadening of the DB over the wide temperature range was observed earlier for large class of both 3D and low-dimensional antiferromagnets as well as for spin-glasses or diluted magnetic systems [6,8,9,[45][46][47]. Therefore, we can examine the temperature variation of DB within the theory for the critical behavior of ESR linewidth due to slowing down of spin fluctuations.…”

Peculiarities of magnetic ordering in the S=5/2 two-dimensional square-lattice antimonate NaMnSbO4

“…Broadening of the ESR line with decreasing temperature has been observed earlier for the wide class of antiferromagnetic, spin-glass and diluted magnetic systems [71][72][73][74][75][76] and explained in the frame of theory of critical behaviour of ESR linewidth in the vicinity of the order-disorder transition.…”