Observation of field-dependent magnetic parameters in the magnetic molecule {Ni4Mo12}

TL;DR

This study reveals that the magnetic parameters of {Ni4Mo12} depend on the magnetic field, indicating possible structural changes affecting spin interactions, as evidenced by magnetic, EPR, and magneto-optical measurements.

Contribution

It introduces a field-dependent model for magnetic interactions in {Ni4Mo12}, challenging traditional fixed-parameter approaches and suggesting structural dynamics influence magnetic behavior.

Findings

Magnetization steps occur at irregular fields.

Field-dependent exchange and anisotropy parameters fit the data best.

Structural changes may influence spin interactions under magnetic fields.

Abstract

We investigate the bulk magnetic, electron paramagnetic resonance, and magneto-optical properties of {Ni4Mo12}, a magnetic molecule with antiferromagnetically coupled tetrahedral {Ni4Mo12} in a diamagnetic molybdenum matrix. The low-temperature magnetization exhibits steps at irregular field intervals, a result that cannot be explained using a Heisenberg model even if it is augmented by magnetic anisotropy and biquadratic terms. Allowing the exchange and anisotropy parameters to depend on the magnetic field provides the best fit to our data, suggesting that the molecular structure (and thus the interactions between spins) may be changing with applied magnetic field.