Investigation of the tricritical point of the ising ferromagnet URhGe by angle-resolved measurements

Magneto-caloric effect and specific heat measurements have been performed on a single-crystalline sample of URhGe, an orthorhombic Ising ferromagnet with a magnetization easy axis c, in high-precision in-situ magnetic field along the b axis. In this compound, first order planes (ferromagnetic wing structure) appear below tri-critical point in the T-H_c-H_b phase diagram. In the present study, we have succeeded in observing a peak of magneto-caloric effect up to 2-3 K, indicating that the tri-critical point is above 2-3 K at least. The result of the specific heat measurements, however, suggests the behavior of the transition does not quantitatively change in wide temperature range between 1.5 and 10 K. The lack of the change makes it difficult to decide the position of TCP, which may locate above 2-3 K at least, clearly from the specific heat measurements.