Abstract
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-Hc-Hb 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.
Highlights
Ferromagnetic (FM) quantum phase transitions in clean metals have attracted much interest because a first-order quantum phase transition is commonly observed at low temperatures below a tricritical point (TCP).[1]
A hysteresis in HR, which is of first order, could not be clearly observed by the present magneto-caloric effect (MCE) measurements
A peak, which is a signature of the first-order transition, was clearly observed by means of the MCE measurements even at high temperature of 2-3 K in the magnetic field along the b axis, suggesting that the tricritical point (TCP) locates above 2-3 K at least
Summary
Ferromagnetic (FM) quantum phase transitions in clean metals have attracted much interest because a first-order quantum phase transition is commonly observed at low temperatures below a tricritical point (TCP).[1] Below the TCP, a FM first-order plane (wings) is expected in the three-dimensional phase diagram This type of “T − p − H phase diagram” has been studied in itinerant FM compounds, such as UGe2, URhAl, UCoGa, and ZrZn2 with pressure as a tuning parameter.[2,3,4,5,6,7] Whereas much theoretical work has been reported, the wings have been studied experimentally to a much less extent because a high-pressure environment is usually required in the observation of the wings. The uranium zig-zag chain with the distance of the nearest neighbor dU−U ∼ 3.5 Å is formed along the a axis
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