Enhanced electrical resistance at the field-induced magnetic transitions in some non-stoichiometric and stoichiometric Tb-based ternary germanides.

We present the magnetic and transport behavior of some Tb compounds, namely TbIrGe(2), TbFe(0.4)Ge(2) and TbCo(0.4)Ge(2). The stoichiometric germanide TbIrGe(2) exhibits at least two distinct magnetic transitions in a close temperature interval around 10 K. Non-stoichiometric compounds, TbFe(0.4)Ge(2) and TbCo(0.4)Ge(2), undergo magnetic ordering around 17 and 19 K, respectively. The magnetic state of these compounds appears to be antiferromagnetic-like. Qualitatively there is a correlation between the field response of the magnetization (M), the magnetoresistance (MR) and the entropy change (ΔS) curve in all three compounds. That is, these Tb compounds exhibit a positive MR and ΔS beyond a magnetic field where M also shows a field-induced transition. On the basis of this correlation, we conclude that magnetic disorder/fluctuations beyond a critical field-a phenomenon called 'inverse metamagnetism'-rather than metamagnetism is induced in these compounds.