Magnetic state in RAgAl (R = Dy, Ho, Er)

Jan Heimann 1Dawid Dunikowski 

1. University of Silesia, August Chełkowski Institute of Physics, Department of Solid State Physics, Uniwersytecka 4, Katowice 40-007, Poland

Abstract

The intermetallics DyAgAl, HoAgAl and ErAgAl were obtained by the Czochralski method from a levitated melt. X-ray powder diffraction measurements have shown that the investigated samples crystallize in CeCu2-type structure (Imma).

The X-ray photoelectron spectra were obtained with a Physical Electronics PHI 5700/660 XPS spectrometer using monochromatized Al Kα radiation.

The magnetic measurements (in static fields of 30-2500 Oe) were carried out in the temperature range 4.2-600 K by the Faraday method. Above 50 K magnetic susceptibility follows Curie-Weiss law with θ parameter 35, 16, and 8 K for DyAgAl, HoAgAl and ErAgAl respectively. The effective magnetic moments per rare earths atom are few percent higher than their free ion values. At low temperatures thermomagnetic effects between ZFC and cooled in field of 2500 Oe (FC) runs exist. The susceptibility vs. temperature for ZFC runs shows a peak at 37, 18 and 13 K for DyAgAl, HoAgAl and ErAgAl respectively.

The ac susceptibility (H = 2 Oe, f = 1 kHz) shows a cusp at 44, 24 and 15 K for DyAgAl, HoAgAl and ErAgAl respectively.

The electrical resistivity has been investigated in the temperature range 4.2-300 K with a current 100 mA. In the liquid helium (4.2 K) the resistivity values are large (2.69 μΩm for DyAgAl, 2.78 μΩm for HoAgAl and 3.39 μΩm for ErAgAl). The temperature dependence of the resistivity of ErAgAl shows local maximum at 12.5 K (3.4 μΩm) followed by minimum at 31 K (3.38 μΩm).

The thermomagnetic effects, cusps in ac and peaks in dc susceptibility indicate the spin glass-like state. We conclude that the disorder in nonmagnetic atoms sublattice of the CeCu2 type structure causes the short mean path of the conduction electrons. The RKKY interactions are reduced to the closest neighbors. The Al and Ag atoms differ enough to disturb the symmetry in neighborhood of rare earths. In connection with reducing the range of the RKKY interactions it leads to concentrated spin glass state.

 

Presentation: poster at E-MRS Fall Meeting 2005, Symposium B, by Jan Heimann
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-22 14:26
Revised:   2009-06-07 00:44