Absence of the Hyperfine Magnetic Field at the Ru Site in Ferromagnetic Rare-Earth Intermetallics

Published

May 3, 2010

Author(s)

D. Coffey, M. DeMarco, P.C. Ho, M. B. Maple, T. Sayles, Jeffrey W. Lynn, Qingzhen Huang, S. Toorongian, M. Haka

Abstract

The Mossbauer Effect(ME) is frequently used to investigate magnetically ordered systems. One usually assumes that the magnetic order induces a hyperfine magnetic field, B_{hyper fine}, at the ME active site. This is the case in the ruthenates, where the temperature dependence of B_{hyper fine}at ⁹⁹Ru sites tracks the temperature dependence of the ferromagnetic or antiferromagnetic order. However this does not happen in the rare-earth intermetallics, GdRu₂ and HoRu₂. Specific heat, magnetization, susceptibility, Mossbauer effect, and neutron diffraction have been used to study the nature of the magnetic order in these materials. Both are found to order ferromagnetically at 82.3 and 15.3 K, respectively. Despite the ferromagnetic order of the rare earth moments in both systems, there is no evidence of a correspondingly large B_{hyper fine}in the Mossbauer spectrum at the Ru site. Instead there is a narrow peak which points to the absence of magnetic order. To understand the surprising absence of a transferred hyper-fine magnetic field, we carried out ab initio calculations which show that spin polarization is present only on the rare-earth site. The electron spin at the Ru sites is effectively unpolarized and, as a result, B_{hyper fine} is very small at those sites. This occurs because the 4d Ru electrons form broad conduction bands rather than localized moments. These 4d conduction bands are polarized in the region of the Fermi energy and mediate the interaction between the localized rare earth moments.

Citation

Physical Review B

Volume

81

Issue

18

Pub Type

Journals

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Keywords

Phonons, Ferrmagnetic Order, Intermetallic, Hyperfine Field, Mossbauer

Citation

Coffey, D. , DeMarco, M. , Ho, P. , Maple, M. , Sayles, T. , Lynn, J. , Huang, Q. , Toorongian, S. and Haka, M. (2010), Absence of the Hyperfine Magnetic Field at the Ru Site in Ferromagnetic Rare-Earth Intermetallics, Physical Review B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=903779 (Accessed December 5, 2024)