The complex electronic phase diagram of single-crystalline R2PdSi3 (R = Ho, Dy) studied by thermal expansion and magnetostriction

Thermal expansion and magnetostriction of single-crystalline R2PdSi3 (R = Ho, Dy) have been investigated by means of high-precision capacitance dilatometry and by specific heat studies. Pronounced anomalies in the uniaxial thermal expansion coefficients αa and αc and in the specific heat cp mark the onset of long-range antiferromagnetic (AFM) order at TN = 7.8(3) K (R = Ho) and TN = 7.9(3) K (R = Dy). The different nature of the ground states in both materials is concluded from opposite signs of the thermal expansion anomalies, i.e., opposite uniaxial pressure dependencies. In both materials, there are Schottky-like entropy and anisotropic length changes which are attributed to crystal field effects and reorientation of the easy magnetic axes. The low-temperature magnetic phase diagrams and the magnetostriction data imply an interplay of single-ion effects and magnetic exchange interaction. Even small magnetic fields yield ferrimagnetic phases via yet unknown intermediate antiferromagnetic (Dy2PdSi3) and ferrimagnetic (Ho2PdSi3) phases.