Magnetic hysteresis loops below $300\mathrm{mK}$ on single crystals of the Mn(II)–nitronyl nitroxide free radical chain $[\mathrm{Mn}{\left(\mathrm{hfac}\right)}_2\left(R\right)\text{−}3\mathrm{MLNN}]$ present abrupt reversals of the magnetization, or avalanches. We show that, below $200\mathrm{mK}$, the avalanches occur at a constant field, independent of the sample, and so propose that this avalanche field is an intrinsic property. We compare this field to the energy barrier existing in the sample and conclude that the avalanches are provoked by multiple nucleation of domain walls along the chains. The different avalanche field observed in the zero field cooled magnetization curves suggests that the avalanche mechanisms are related to the competition between ferromagnetic and antiferromagnetic orders in this compound.

• Received 6 April 2007

DOI:https://doi.org/10.1103/PhysRevB.77.064416