Spatial Determination of Magnetic Avalanche Ignition Points

TL;DR

This study uses time-resolved local magnetization measurements to locate the ignition points of magnetic avalanches inside Mn12-ac crystals, revealing they originate from small internal regions rather than edges.

Contribution

It introduces a method to spatially determine internal avalanche ignition points in molecular magnets using spherical bubble growth assumptions.

Findings

Avalanches originate from small internal regions (~150 microns radius).

The propagation fronts are curved, indicating non-linear growth.

Ignition points are not at the edges but inside the crystal.

Abstract

Using time-resolved measurements of local magnetization in the molecular magnet Mn12-ac, we report studies of the propagation of magnetic avalanches (fast magnetization reversals) that originate from points inside the crystals rather than at the edges. The curved nature of the fronts produced by avalanches is reflected in the time-of-arrival at micro-Hall sensors placed at the surface of the sample. Assuming that the avalanche interface is a spherical bubble that grows with a radius proportional to time, we are able to locate the approximate ignition point of each avalanche in a two-dimensional cross-section of the crystal. For the samples used in these studies, avalanches in a given crystal are found to originate in a small region with a radius of roughly 150 microns.