Critical indices of magnetic phase transitions as indicators of the topology of exchange interaction in holmium films

Transitions between different types of spin ordering in holmium films have been studied in the temperature range 10–140 K and magnetic fields 0–4 T. The magnetic phase diagram in H–T coordinates indicates the presence of transitions between intermediate helicoid phases from the helix state to such spin structures, such as ferromagnet (ferro), fan (fan) and sliding structures (spin-slip). Arrott's method made it possible to determine the critical indices for each of the transitions. Based on the critical indices, a selection of models and their combinations applicable to describe the mentioned non-collinear spin states was made.