Wing structure in the phase diagram of the Ising ferromagnet URhGe close to its tricritical point investigated by angle-resolved magnetization measurements

Abstract

High-precision angle-resolved dc magnetization and magnetic torque studies were performed on a single-crystalline sample of URhGe, an orthorhombic Ising ferromagnet with the c axis being the magnetization easy axis, in order to investigate the phase diagram around the ferromagnetic (FM) reorientation transition in a magnetic field near the b axis. We have clearly detected first-order transition in both the magnetization and the magnetic torque at low temperatures, and determined detailed profiles of the wing structure of the three-dimensional T -H b -Hc phase diagram, where Hc and H b denotes the field components along the c and the b axes, respectively. The quantum wing critical points are located at µ0Hc ∼ ±1.1 T and µ0H b ∼13.5 T. Two second-order transition lines at the boundaries of the wing planes rapidly tend to approach with each other with increasing temperature up to ∼ 3 K. Just at the zero conjugate field (Hc = 0), however, a signature of the first-order transition can still be seen in the field derivative of the magnetization at ∼ 4 K, indicating that the tricritical point exists in a rather high temperature region above 4 K. This feature of the wing plane structure is consistent with the theoretical expectation that three second-order transition lines merge tangentially at the triciritical point.

Non-unitary triplet superconductivity tuned by field-controlled magnetization --URhGe, UCoGe and UTe$_2$--

“…We assume this picture applicable to the other compounds too. When the applied field direction is rotated from the b-axis toward the easy axis c by the angle θ, the magnetization curves are measured by Nakamura, et al 64 . It is obvious that the measured magnetization M (θ) contains the contribution from the spontaneous moment M c projected onto the applied field direction, that is, M c sin(θ).…”

“…This is confirmed experimentally at least lower fields up to H < 5T and T =2K 65 . Thus in this situation, we can extract the M b (H) curves by simply subtracting the contribution M c sin(θ) from the measured data 64 . The result is shown in Fig.…”

Electrical Transport under Pressure in Non-centrosymmetric URhSn

“…In antiferromagnetic systems, a QCP has been achieved in several systems while a ferromagnetic QCP remains elusive [1]. In itinerant ferromagnetic systems generally a second-order phase transition turns into first-order at a tri-critical point (TCP) and forms so-called first order "wing structure" in temperaturepressure-field (T -P-H) phase diagram, eventually terminating at a quantum-critical-end point (QCEP) in magnetic field [1][2][3][4][5]. Another tuning parameter could be crystallographic orientation in strongly anisotropic magnets as in the case of URhGe [5,6].…”

Anomalous Anisotropy of the Lower Critical Field and Meissner Effect in UTe2

“…However, the transverse field configuration with H b attracted most attention, due to the observation of a strong field-induced reinforcement of SC on approaching the metamagnetic field H m ≈ 35 T. [13][14][15][16] Most of the published magne-tization data in FM SC deal with the field dependence of the FM interaction in longitudinal or transverse field scan. [17][18][19].…”