In a paper recently published in the journal Physical Review Letters, our colleagues Virna Kisiček, Damir Dominko, Matija Čulo, Mirta Herak and Tomislav Ivek, together with former PhD students Željko Rapljenović and Martina Dragičević and other collaborators, highlighted the role of spin reorientation in the magnetoelectric effect observed in antiferromagnetically ordered cuprate Cu₃TeO₆ investigated using static polarization measurements in an external magnetic field. Published results demonstrate that the mentioned material represents perhaps a unique system for studying the interplay of several key phenomena in spintronics.

Spin-Reorientation-Driven Linear Magnetoelectric Effect in Topological Antiferromagnet Cu₃TeO₆

Virna Kisiček, Damir Dominko, Matija Čulo, Željko Rapljenović, Marko Kuveždić, Martina Dragičević, Helmuth Berger, Xavier Rocquefelte, Mirta Herak, and Tomislav Ivek, Phys. Rev. Lett. 132, 096701 (2024).

DOI: 10.1103/PhysRevLett.132.096701

Antiferromagnets are magnetic materials in which the magnetic order, unlike in ferromagnets, does not produce an external magnetic field. Nevertheless, antiferromagnetic materials have great potential for applications in future electronic devices. This is recognized through the new field of antiferromagnetic spintronics whose goal is to control the spins in the antiferromagnet, which would be used to increase the speed and density of data recording in new electronic devices, with potentially high energy efficiency. The strong interaction energy of magnetic moments in antiferromagnets corresponds to excitations at high frequencies, even in the THz range. Manipulation of electronic states in the terahertz range would allow for an increase in read/write speeds by several orders of magnitude compared to the current ones. In addition, magnetoelectrics stand out, in which antiferromagnetism can be controlled by an electric field, or voltage, which opens up the possibility of increasing the energy efficiency of electronic devices by several orders of magnitude. Also interesting are antiferromagnets with topological spin excitations, which have great potential for application in magnonics and topological spintronics.

Cu₃TeO₆ is a cubic material with an unusual and unique magnetic lattice in which the copper spins order antiferromagnetically below the temperature of 61K, which was first demonstrated by M. Herak and colleagues almost two decades ago. Recently, it was observed that in the magnetically ordered state of this material, the magnon bands overlap in the topological Dirac points, leading to the discovery of topological magnons in a three-dimensional system. In this paper, V. Kisiček and colleagues showed that Cu₃TeO₆ is a magnetoelectric in which the static electric polarization is induced by an external magnetic field (Figure 1a and 1b). However, different behavior of the induced polarization in the magnetic field was observed for crystallographically equivalent directions, which is why the magnetic response in the same range of magnetic fields was studied in detail and the existence of spin reorientation in the magnetic field was experimentally determined. With the help of a phenomenological model based on the previously known Hamiltonian of this system, the magnetic structures in the applied magnetic field and the magnetic point groups of these structures, which differ from the previously known ground-state symmetry, were calculated (Figure 1c). Additionally, the obtained magnetic point groups are polar, but the corresponding structures are slightly different from the similar nonpolar structures, which is why the observed magnetoelectric effect is dominantly linear (Figure 1b). All these properties make this compound possibly a unique material in which the interplay of different potentially useful properties can be studied: antiferromagnetism, magnetoelectricity, spin reorientation and topological spin excitations.