Uniaxial-Stress-Induced Ferromagnetism in the Itinerant Metamagnetic Compound UCoAl Probed by Magnetostriction Measurements

Magnetostriction measurements for the Ising-type itinerant metamagnetic compound UCoAl were performed under uniaxial stress for sigma parallel to c-axis using an in situ pressure-tuning device. A ferromagnetic transition was clearly observed at zero magnetic field at least above similar to 0.05 GPa. For a stress of 0.1 GPa, the FM transition is of 2nd order, since the anomaly of the thermal expansion coefficient does not show any hysteresis at the transition. No step like behavior was observed for the FM transition under uniaxial stress in the present study. From the precise stress dependence of T-C, a change of the power (n) law from 3/4 to 1/2 was also found at around 0.1 GPa for the expression of T-C(sigma) proportional to (sigma -sigma(c))(n), where the critical value is sigma(c) similar to 0.026 GPa.