Ni2+–Ni2+ exchange interaction in the high-pressure phase of MgSiF6·6H2O crystal

The spin-spin interaction between pairs of paramagnetic ions of bivalent nickel is studied experimentally in MgSiF6 · 6H2O single crystals in the high-pressure phase (R3) at a frequency of 36 GHz at 4.2 K. It is shown that the electron paramagnetic resonance spectrum belongs to the nearest pair of Ni ions. The interaction is described by the term S1K^S2 of the spin Hamiltonian. The components of the tensor K^ include isotropic exchange and magnetic dipole-dipole interactions. It is found that the exchange interaction in the phase under investigation is of the ferromagnetic type and increases linearly with pressure: J = – 580–22P.

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