R. Kiefe | Searcharxiv

arXiv2026

Finite-temperature micromagnetic model bridging atomic- and macro-scale magnetism

A multi-scale finite-temperature micromagnetic model is presented, based on the Landau-Lifshitz equation and the Bernoulli differential equation. This model accurately reproduces classic Maxwell magnetostatics of paramagnets for high temperatures and accurately reproduces standard micromagnetics described by the conventional Landau-Lifshitz model in ferromagnets. The Landau-Lifshitz-Bernoulli (LLBe) model can, by design, directly couple atomic-scale simulations with micromagnetics and output consistent predictions of bulk magnetic properties at finite temperatures, from below to above the material's Curie temperature. The LLBe model is validated against established solvers: MUMAX3 for zero-temperature micromagnetics, and FEMCE for high-temperature classic magnetostatics. We present an application of the LLBe model by simulating Heat-Assisted magnetic recording on a thin magnetic track with local heating, demonstrating the multi-scale finite-temperature capabilities of the LLBe.

cond-mat.mtrl-sci↗

arXiv2024

On correctly assessing the reversibility of the magnetocaloric effect from indirect measurements

The adiabatic temperature change ($\Delta T_{ad}$) of a magnetic refrigerant can be indirectly estimated through field ($H$) and temperature ($T$) dependent magnetization ($M$) and specific heat ($C_p$) measurements. A direct integration approach for this estimation is frequently reported, which is an approximation to a rigorous mathematical approach. In this work, we propose an iterative method in small $H$ steps, to estimate $\Delta T_{ad}$ from indirect measurements. We show that this approach is able to reproduce the reversibility of the magnetocaloric effect, and provides a more accurate estimation of $\Delta T_{ad}$, up to 10\% when considering a detailed $M(H,T)$ and $Cp(H,T)$ dataset that reproduces the magnetothermal properties of gadolinium, a benchmark room-temperature magnetic refrigerant.

cond-mat.mtrl-sci↗