# SKM 2023 – wissenschaftliches Programm

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# MA: Fachverband Magnetismus

## MA 46: Ultrafast Magnetization Effects II

### MA 46.5: Vortrag

### Freitag, 31. März 2023, 10:30–10:45, HSZ 02

Dynamics of the Morin transition in hematite — •Maik Kerstingskötter^{1}, Tobias Dannegger^{1}, András Deák^{2}, László Szunyogh^{2,3}, and Ulrich Nowak^{1} — ^{1}Department of Physics, University of Konstanz — ^{2}Department of Theoretical Physics, Budapest University of Technology and Economics — ^{3}ELKH-BME Condensed Matter Research Group, Budapest University of Technology and Economics

Below a critical temperature T_{M} of about 264 K, hematite is a perfect antiferromagnet with zero net magnetization due to the fact that the spins of the four sublattices are antiparallel and aligned with the c-axis. If the temperature exceeds this critical point, the spins reorient into the basal plane and assume a small canting angle that results in a finite net magnetization. This first-order phase transition from the antiferromagnet to the weak ferromagnetic phase is the Morin transition. While the equilibrium properties are well known, we want to investigate the nonequilibrium dynamics of the transition. Here we use atomistic spin dynamics simulations on the basis of an ab initio model to study the system’s response to an instantaneous temperature increase from T<T_{M} to T>T_{M}. In the model used, we indeed observe this Morin transition, which takes place in the range of five to a few hundred picoseconds, depending on the size of the Gilbert damping used.