Control and generation of domain walls near magnetic compensation in ferrimagnetic CoTb via applied thermal gradient

Recently, the manipulation of domain walls using magnetic field [1] spin polarized current [2] electric field [3] and temperature gradient [4] have attracted significant interest. This control of domain wall nucleation and propagation could lead to new advances in the field of data storage [5] and magnetic logic [6]. Here we report on the use of a thermal gradient to nucleate, propagate and annihilate well-defined domain walls. The domain walls are created in lithographically patterned wires of amorphous, ferrimagnetic CoTb alloy thin films. The net magnetization of these films is defined by the competition between the magnetization of the antiferromagnetically coupled Co sublattice and Tb sublattice. For some compositions, there exists a given temperature known as the compensation temperature (T_comp), where the net saturation magnetization of the sample is zero due to the equal magnitude and opposite direction of the two competing sublattice moments. Below T_comp, the net magnetization of the film aligns along the dominant Tb magnetization, while above T_comp the direction of the magnetization is controlled by the Co sublattice. By crossing this compensation temperature under applied field, it is possible to change the dominant sublattice - creating a shift in the net magnetization direction of the film.