Multiple magnetic interactions and large inverse magnetocaloric effect in TbSi and TbSi 0.6 Ge 0.4
We present a comprehensive investigation of the electronic structure, magnetization, specific heat, and crystallography of TbSi (FeB structure type) and TbSi 0.6 Ge 0.4 (CrB structure type) compounds. Both TbSi and TbSi 0.6 Ge 0.4 exhibit two antiferromagnetic (AFM) transitions at T N1 ≈ 58 and 57 K, and T N2 ≈ 36 and 44 K, respectively, along with an onset of weak metamagneticlike transition around 6 T between T N1 and T N2 . High-resolution specific heat (C P ) measurements show the second- and first-order nature of the magnetic transition at T N1 and T N2 , respectively, for both samples. However, in the case of TbSi, the low-temperature (LT) AFM to high-temperature (HT) AFM transition takes place via an additional AFM phase at the intermediate temperature (IT), where both LT to IT AFM and IT to HT AFM phase transitions exhibit a first-order nature. Both TbSi and TbSi 0.6 Ge 0.4 manifest significant magnetic entropy changes (ΔS M ) of 9.6 and 11.6 J/kg-K, respectively, for Δμ 0 H=7 T, at T N2 . The HT AFM phase of TbSi 0.6 Ge 0.4 is found to be more susceptible to the external magnetic field, causing a significant broadening in the peaks of ΔS M curves at higher magnetic fields. Temperature- and field-dependent specific-heat data have been utilized to construct the complex HT phase diagram of these compounds. As a result, temperature-dependent x-ray diffraction measurements demonstrate substantial magnetostriction and anisotropic thermal expansion of the unit cell in both samples.