Magnetoelastic coupling and phases in the skyrmion lattice magnet Gd2PdSi3 discovered by high-resolution dilatometry

We report detailed thermodynamic studies on high-quality single crystals of the centrosymmetric skyrmion-hosting intermetallic Gd2PdSi3 by means of high-resolution capacitance dilatometry in fields up to 15 T which are complemented by specific heat and magnetization studies. Our dilatometric measurements show magnetoelastic effects associated with antiferromagnetic order at TN1 = 22.3 K and TN2 = 19.7 K, as well as strong field effects in an applied magnetic field of 15 T up to 200 K (150 K) for B ‖ c (B ‖ a*, i.e. B ⊥ c). The data allow us to complete the magnetic phase diagram, including a new feature at T ∗ ≈ 12 K below which a new degree of freedom becomes relevant. For the first time, the magnetic B vs. T phase diagram for the a*-axis is also reported. Grüneisen analysis shows the onset of magnetic contributions around 60 K, i.e., well above TN1. Uniaxial pressure dependencies of opposite sign, −1.3 K/GPa and 0.3 K/GPa, are extracted for the out-of-plane and in-plane directions at TN1. For T ∗ we obtain ∂T /∂pc = 1.4 K/GPa. In particular we elucidate thermodynamic properties of the recently discovered skyrmion lattice phase and show that it is strongly enhanced by uniaxial pressure. 1 ar X iv :2 10 4. 13 31 1v 1 [ co nd -m at .s tr -e l] 2 7 A pr 2 02 1