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

Abstract

We present the magnetic and transport behavior of some Tb compounds, namely TbIrGe₂, TbFe_0.4Ge₂ and TbCo_0.4Ge₂. The stoichiometric germanide TbIrGe₂ exhibits at least two distinct magnetic transitions in a close temperature interval around 10 K. Non-stoichiometric compounds, TbFe_0.4Ge₂ and TbCo_0.4Ge₂, 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.