Magnetoelectric Effect and Metamagnetic Transitions in Dy AlO3

The magnetoelectric (ME) effect has been studied as a function of applied magnetic field ($\overrightarrow{\mathrm{H}}$) in a crystal of metamagnetic Dy Al${\mathrm{O}}_3$. The ME signal at a frequency of 150 Hz was measured along the [001] direction of the orthorhombic unit cell at temperature $T=(1.45\mathrm{}\pm 0.05)°$K. Two types of metamagnetic transitions were studied. The first involved a reversal on a single magnetic sublattice in $\overrightarrow{\mathrm{H}}\parallel \mathrm{}\left[110\right]\mathrm{}$. while the second involved the simultaneous reversal of two of the four magnetic sublattices in $\overrightarrow{\mathrm{H}}\parallel \mathrm{}\left[010\right]\mathrm{}$. The ME signal decreased abruptly at the critical fields (≈ 6 kOe) for metamagnetic transitions, as determined from magnetization measurements on the same sample. In agreement with simple physical arguments, the ME susceptibility was found approximately to scale with the number of antiferromagnetic spins in the material. The experimental data were compared to theoretical curves and the results were discussed in terms of magnetic point symmetries.