Burst-like features observed from different techniques at the first-order magnetic transition of La(Fe,Co,Si)13

Abstract

La(Fe,Si)13 alloys are prone to display burst-like phenomena at their first-order ferromagnetic transition, such as a latent heat decomposed into a succession of heat flux avalanches. For some extreme cases, these phenomena are so pronounced that they can yield recalescence/antirecalescence events. It turns out that these features are also highly sensitive to the technical specificities of the employed measurement systems. Here, we compare the thermal events at the first-order magnetic transition of LaFe11.4Si1.31Co0.29 using magnetization, two differential scanning calorimeters and a thermometry probe specially designed for the present study. These techniques are complementary to each other, and allow to make a distinction between the properties influenced by thermal coupling and those more intrinsic to the compound or to the sample. A simple thermal model is built to account for the thermal lags in the different devices, and to provide insights into the dependence of the duration of the transition on the thermal sweep rate. Looking in closer detail at the development of the transition, we found evidence of a rate independent initial regime, followed by a second one along which the same shape of temporal profile is spread over a more or less long duration depending on the sweep rate. Possible underlying mechanisms corresponding to these regimes are discussed.