Hyperfine interactions in intermetallic rare earth-gallium compounds studied by 111 Cd PAC
- PDF / 468,492 Bytes
- 6 Pages / 439.37 x 666.142 pts Page_size
- 73 Downloads / 149 Views
Hyperfine interactions in intermetallic rare earth-gallium compounds studied by 111 Cd PAC F. H. M. Cavalcante · L. F. D. Pereira · H. Saitovitch · J. Mestnik-Filho · A. F. Pasquevich · M. Forker
Published online: 2 November 2012 © Springer Science+Business Media Dordrecht 2012
Abstract Magnetic and electric hyperfine interaction of the nuclear probe 111 In/ 111 Cd in intermetallic compounds of the rare earth-gallium system have been investigated by perturbed angular correlation (PAC) spectroscopy. The PAC measurements, supported by X-ray diffraction, provide evidence for a marked phase preference of 111 In for hexagonal RGa2 over orthorhombic RGa and of RGa3 with the L12 structure over RGa2 . In the case of SmGa2 , the magnetic hyperfine field Bhf , the electric quadrupole interaction and the angle β between Bhf and the symmetry axis of the electric field gradient have been determined as a function of temperature. The angle β = 0 is consistent with the results of previous magnetization studies. Up to T ≤ 17 K the magnetic hyperfine field has a constant value of Bhf = 3.0(2) T. The rapid decrease at higher T gives the impression of a first-order transition with an order temperature of TN = 19.5 K. In the RKKY model of indirect 4 f interaction the
F. H. M. Cavalcante (B) · L. F. D. Pereira · H. Saitovitch · M. Forker Centro Brasileiro de Pesquisas Físicas, CBPF, Rio de Janeiro, Brazil e-mail: [email protected] F. H. M. Cavalcante · J. Mestnik-Filho Instituto de Pesquisas Energéticas e Nucleares, IPEN-CNEN, São Paulo, Brazil A. F. Pasquevich Departamento de Física, Facultad de Ciencias Exactas, UNLP, La Plata, Argentina A. F. Pasquevich Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, Buenos Aires, Argentina M. Forker Helmholtz Institut für Strahlen-und Kernphysik, Universität Bonn, Bonn, Germany
124
F.H.M. Cavalcante et al.
ratio TC /Bhf (0) is a measure of the coupling constant. For 111 Cd:SmGa2 (TC /Bhf (0) ∼ 6.5 K/T) this ratio is significantly smaller than for the same probe in other R intermetallics (SmAl2 ∼ 9.5 K/T, Sm2 In ∼ 13.5 K/T). Keywords Magnetic hyperfine interaction · Rare earth gallium intermetallic compounds · Perturbed angular correlations
1 Introduction The phase diagrams of gallium with the rare earth (R) metals R = Ce, Pr, ..., Gd, Tb, ..., Er, Tm contain up to 6 intermetallic compounds [1, 2]. All R constituents form the phases RGa6 , RGa2 , RGa, and R5 Ga3 . The phases RGa3 and R3 Ga5 are found only for the heavy rare earth R = Tb, Dy, . . . , Tm, R3 Ga only for the light R = Ce, Pr, Nd and Sm. At low temperatures long-range RKKY exchange coupling mediated by the conduction electrons leads to spontaneous magnetic order of the localized 4 f -moments in most of these intermetallics [3–6]. The spin polarization of the conduction electrons produces a Fermi contact hyperfine field Bhf at nuclear sites. Measurements of Bhf are therefore a valuable source of information on the exchange interaction and are also a useful tool for the investigation of phase transition
Data Loading...
