On the local magnetic moments of transition-metal Mössbauer impurities in ferromagnetic rare earths

Abstract

Using isomer shift and hyperfine data of transition-metal Mössbauer impurities 193Ir and 57Fe diluted in the ferromagnetic rare-earth hosts Gd, Tb, and Dy, the formation of local moments at these impurities based on a two-band (s-d) model in the framework of an extended Ruderman-Kittel-Kasuya-Yosida picture is theoretically discussed. The experimental data of Mössbauer isomer shifts and hyperfine fields at the nobel probe 197Au placed in Gd, Tb, and Dy are also briefly discussed, based on an extended Daniel–Friedel model. The results exhibit a good agreement with the available experimental measurements.

Calculated hyperfine fields of 3d and 4d impurities in Co HCP

“…The magnetic hyperfine field of impurities in ferromagnetic hosts has been on the focus of both experimental and theoretical investigations to study the magnetism in condensed matter from an atomic scale, [1][2][3][4][5][6][7][8][9][10][11][12][13]. Nowadays, a large amount of experimental data provided by several experimental techniques are available for various metallic hosts.…”

The hyperfine field at rare-earth impurities diluted in Fe, Co and Ni hosts: a theoretical study

“…Here for the sake of numerical simplicity we take the s-p magnetic moment at the impurity site mc (0) as proportional to the d host magnetization [29], i.e., mc (0) = −γ m d , with the proportionality constant γ of the order of 0.1. A 5d cp and A 4f cp are the 5d and 4f core polarization coupling parameters respectively [8,14,30]. Here we take A 5d cp = −100 T/µ B and A 4f cp = −150 T/µ B [8,13,30].…”

“…The formation of local moments and its connection to the hyperfine interactions is one of the central problems in the description of the magnetic properties of metals [1][2][3][4][5][6][7]. In particular, many theoretical works based either on first-principles calculations or on model approaches have been devoted to the study of the systematics of the magnetic moments and the hyperfine fields at impurity sites diluted in ferromagnetic transition metals and rare-earth hosts [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Very recently, we have extended a theoretical formulation including the change in the energy of the hopping between the impurity and the nearest neighbours [23][24][25] to study the local magnetic moments and the hyperfine fields at La, Gd and Lu impurities diluted in Fe and Ni ferromagnetic hosts [22].…”

Magnetic hyperfine field at dilutedFe57in vapor-quenched heavy-rare-earth films

“…One can see from this figure that the measured B hf values for substitutional Fe in different RE metals scales with the de Gennes factor, while the corresponding one for interstitial Fe do not show any systematic behavior: the hf field at interstitial Fe in RE matrices seems to have an average B hf value of 1.9 T. Dunlap et al 20 have pointed out that deviations from the linear relation between B hf and (g J Ϫ1)J, for a substitutional nonmagnetic impurity, can occur due to the effects of the nonzero angular momentum on the exchange interaction between the localized 4 f moments and the conduction electrons, i.e., contributions due to orbital and spin-dipolar interactions. On the other hand, Leal and Troper 21 have discussed the different contributions to B hf using a model based on an extended RKKY theory. In our case, the deviations from the standard RKKY theory could be even larger due to the fact that we have a magnetic impurity located at an interstitial site, where the pressure effect is expected to be more relevant.…”