Emergence of partially disordered antiferromagnetism and isothermal magnetization plateau due to geometrical frustration in a metallic compound, Er2RhSi3

Partially disordered antiferro (PDA) magnetism (in which one of the three magnetic ions in a triangular network remains magnetically disordered), has been known commonly among geometrically frustrated insulating materials. The one-third plateau in isothermal magnetization (M) of such materials has been of great theoretical interest. Here, we report these properties in a AlB2-structure derived metallic material, Er2RhSi3 in which Er sublattice has triangular networks. The presence of a well-defined lamda anomaly in the temperature (T) dependence of heat capacity and its magnetic-field (H) dependence, and the loss of spin-disorder contribution in electrical resistivity (rho) confirm antiferromagnetic order below (TN=) 5 K. On the other hand, the separation of zero-field-cooled and field-cooled dc magnetic susceptibility (chi) curves, decay of isothermal remnant magnetization and the frequency dependence of real and imaginary components of ac chi suggest the onset of spin-glass freezing concomitant with the antiferromagnetic order. In addition, interestingly, we observe one-third plateau in M(H) below 20 kOe for T less than TN. The change in rho as a function of H at a given temperature well below TN is also revealing, with this compound exhibiting a plateau below 20 kOe, with complexities at higher fields. Therefore, this compound serves as a prototype for theoretical understanding of transport behavior across one-third plateau due to PDA magnetism in a metal without any interference from the 4f delocalization phenomena.