Magnetic phase transitions in layered perovskites K₂CoF₄ and K₂NiF₄

Abstract

For the first time we have calculated low-energy electronic structure both in paramagnetic and magnetic state as well as zero-temperature properties and thermodynamics of K₂CoF₄ and K₂NiF₄. We consistently described that magnetic properties of these compounds are in agreement with its insulating ground state. The orbital moment of 1.06 μ _B gives 30% contribution to the total moment of K₂CoF₄ of 3.25 μ _B at T = 0 K. From this low-energy electronic structure we have calculated the temperature dependence of the specific heat with a λ-type peak marking the magnetic phase transition. In our ionic approach, K₂CoF₄ and K₂NiF₄ are independent insulators on distortions and the magnetic order.

Keywords:

• K₂CoF₄
• K₂NiF₄
• electronic structure
• crystal field
• magnetic phase transition