Effective decoupling of ferromagnetic sublattices by frustration in Heusler alloys

Magnetic frustration in ferromagnetic metallic systems is unusual due to the long-range and symmetric nature of the exchange interactions. In this work we prove that it is possible to obtain a highly frustrated ferromagnetic phase in a multisublattices cubic structure through a fine-tuning of the magnetic interactions. This peculiar state is achieved in Ni-Mn-(In, Sn) Heusler alloys and results in the effective decoupling of their two intertwined ferromagnetic sublattices. One sublattice is ferromagnetic long-range ordered below the macroscopic Curie temperature (TC) whereas the second one remains disordered until a crossover to a polarized state occurs at T  TC. This result points out that a fine engineering of the magnetic interactions in metallic systems can lead to interesting novel and emergent phenomena.