Magnetic-field-induced structural transformation in Er5Si4

Magnetization and magnetostriction measurements in pulsed magnetic fields reaching 600 kOe reveal strong magnetoelastic effects in Er5Si4 at low temperature. A clear hysteretic behavior of the magnetization isotherms and sharp first-order-type anomalies of magnetostriction are observed. Neutron powder diffraction experiments carried out in steady magnetic fields ranging from 0 to 50 kOe confirm that both the magnetization and magnetostriction anomalies are associated with a reversible magnetic-field-induced crystallographic transformation at low temperature. The low-temperature crystal structure of Er5Si4 is monoclinic in a zero field but the application of a strong magnetic field (H>80 kOe at T=5 K) induces an orthorhombic phase, which is known as the ground state of numerous other compounds in the extended 5:4 family of materials. The existence of a magnetic-field-induced crystallographic transformation without the change of the magnetic state of the material is an unusual property of magnetic solids, and to our knowledge this is the first time that such an anomaly is observed in the 5:4 intermetallic materials.