UNSPECIFIED. (2000) Crossover from low-dimensional to three-dimensional ferromagnetism in CePd1-xPtxSb alloys. PHYSICAL REVIEW B, 61 (2). pp. 1232-1239. ISSN 1098-0121

Abstract

The hexagonal material CePdSb exhibits low-dimensional ferromagnetism with T-c = 17.5, while isostructural CePtSb shows normal three-dimensional ferromagnetism with T-c = 4.8 K. To understand the low-dimensional ferromagnetic ordering of CePdSb we have investigated CePd1-xPtxSb alloys, using ac susceptibility, heat capacity, thermal expansion, and zero-field spin-echo NMR measurements. The ac susceptibility shows that the T-c of the Pd-rich alloys is higher than that expected from a linear extrapolation of the Pt-rich alloys. The heat capacity shows a smooth crossover from the anomalous (x less than or equal to 0.4) to normal (x greater than or equal to 0.6) ferromagnetic behavior with increasing Pt concentration. Thermal expansion results agree with the heat-capacity data for the alloys that are either Pd rich (x less than or equal to 0.2) or Pt rich (x greater than or equal to 0.8). However, the thermal expansion shows anomalous behavior for the alloys x = 0.4 and 0.6, in the composition range where the heat capacity exhibits the crossover behavior. From the heat capacity and ac susceptibility measurements a phase diagram, temperature vs x, for CePd1-xPtxSb alloys has been proposed. Low power zero-field Sb spin-echo NMR studies show well-defined quadrupole split NMR spectra in both CePdSb and CePtSb, confirming the ferromagnetic ground state. Only a very broad NMR signal has been observed in the substituted alloys of CePd1-xPtxSb (0.1 less than or equal to x less than or equal to 0.8) because of the differences between the quadrupole splitting of CePtSb and CePdSb. The internal field at the Sb nucleus at low temperatures for CePtSb(CePdSb) is +2.3 T (+2.8 T) and the quadrupole splitting 8.5 and 5.1 MHz (3.8 and 2.3 MHz) for Sb-121 and Sb-123, respectively.

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