Magnetoelectric and Magnetostrictive Effects in Scheelite-Type HoCrO.

Scheelite-type HoCrO was prepared by treating the ambient-pressure zircon-type precursor phase under 8 GPa and 700 K. A long-range antiferromagnetic phase transition is found to occur at ≈ 23 K due to the spin order of Ho and Cr magnetic ions. However, the antiferromagnetic ground state is sensitive to an external magnetic field and a moderate field of about 1.1 T can induce a metamagnetic transition, giving rise to the presence of a large magnetization up to 8.5 μ/f.u. at 2 K and 7 T. Considerable linear magnetoelectric effect is observed in the antiferromagnetic state, while the induced electric polarization experiences a sharp increase near the critical field of the metamagnetic transition. Ferromagnetism and ferroelectricity thus rarely coexist under higher magnetic fields in scheelite-type HoCrO. Moreover, a magnetic field also plays an important role in the longitudinal constriction of HoCrO, and a significant magnetostrictive effect with a value of up to 300 ppm is observed at 2 K and 9 T, which can be attributed to the strong anisotropy of the rare-earth Ho ion. Possible coupling between magnetoelectric and magnetoelastic effects is discussed.