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

Partially disordered antiferromagnetism (PDA) (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 1/3 plateau in isothermal magnetization M of such materials has been of great theoretical interest. Here we report these properties in an ${\mathrm{AlB}}_{2}$-structure-derived metallic material, ${\mathrm{Er}}_{2}\mathrm{Rh}{\mathrm{Si}}_{3}$, in which the Er sublattice has triangular networks. The presence of a well-defined \ensuremath{\lambda} anomaly in the temperature T dependence of heat capacity and its magnetic-field H dependence and the loss of spin-disorder contribution to electrical resistivity \ensuremath{\rho} confirm antiferromagnetic order below ${T}_{N}=5\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. On the other hand, the separation of zero-field-cooled and field-cooled dc magnetic susceptibility \ensuremath{\chi} curves, the decay of isothermal remnant magnetization, and the frequency dependence of real and imaginary components of ac \ensuremath{\chi} suggest the onset of spin-glass freezing concomitant with the antiferromagnetic order. In addition, interestingly, we observe the 1/3 plateau in M(H) below 20 kOe for $T<{T}_{N}$. The change in \ensuremath{\rho} as a function of H at a given temperature well below ${T}_{N}$ 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 the 1/3 plateau due to PDA magnetism in a metal without any interference from the $4f$ delocalization phenomenon.