Electric current induced rupture in a permalloy strip

In this work, we test the thermal rupture of a permalloy strip when an electric current is flowing through the strip. For a strip with the top surface exposed to air or covered with a thin insulating layer, we find that the strip gets destroyed at a DC density of only ∼0.6 × 1012 A/m2 and a temperature smaller than 400 K, while it can withstand ∼1.5 × 1012 A/m2 and ∼1200 K if the current is delivered in a sub-μs pulse. If the permalloy strip is covered with a heat dissipation window of Ta2O3/Pt or Ta2O3/Au, so the permalloy can also conduct heat through the top surface, the strip can withstand ∼3.5 × 1012 A/m2 and ∼2000 K. Interestingly, the strips always break in a section not covered by the dissipation window, even if that is not the hottest part of the strip. Therefore, the layers forming the dissipation window help with not only extracting the heat but also delaying the structural damage.