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

The polycrystalline intermetallics DyAgAl, HoAgAl and ErAgAl were obtained from a levitated melt. X-ray powder diffraction confirmed single-phase 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 35–2100 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 slightly higher than their free ion values. At low temperatures thermomagnetic effects between ZFC and cooled in field of 2500 Oe (FC) runs exist. The dc susceptibility versus temperature for ZFC runs shows a peak at 37, 18 and 13 K for DyAgAl, HoAgAl and ErAgAl, respectively. The ac susceptibility 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. In the liquid helium (4.2 K) the resistivity values are large (2.69 μΩ m for DyAgAl, 2.78 μΩ m for HoAgAl and 3.39 μΩ m for ErAgAl). The temperature dependence of the resistivity of ErAgAl shows local maximum at 12.5 K (3.4 μΩ m) followed by minimum at 31 K (3.38 μΩ m). The thermomagnetic effects, cusps in ac and peaks in dc susceptibility indicate the spin glass state. HoAgAl may be considered as a cluster glass material. Disorder in nonmagnetic atoms sublattice causes the short mean path of the conduction electrons. The RKKY interactions are reduced to the closest neighbors. Randomly distributed 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 NMAD driven spin glass state.