[Paper Review] 3D time-resolved analysis of the evolution metamagnetic phase transition in FeRh system

Aleksei S. Komlev, Rodion A. Makarin+7 more|arXiv (Cornell University)|Nov 29, 2022

Magnetic Properties and Applications4 citations

TL;DR

This study presents a 3D time-resolved analysis of the metamagnetic phase transition in FeRh, revealing the nucleation, growth, and merging of ferromagnetic clusters during the antiferromagnetic-to-ferromagnetic transition. Using in situ magnetization measurements, the authors identify distinct kinetic stages and attribute changes in growth rate to the magnetocaloric effect and limitation effects, with microstructure-dependent transition mechanisms.

ABSTRACT

The FeRh alloy is an attractive material for studies of magnetic first-order phase transitions. The phase transition in FeRh from an antiferromagnetic to the ferromagnetic state is accompanied by the nucleation, growth, and merging of ferromagnetic clusters. The ferromagnetic phase evolution is studied in detail, and its various stages are distinguished. Both static properties and phase transition kinetics (time dependences of magnetization) are investigated. A comprehensive analysis allows us to determine the ferromagnetic phase nucleation regions and the main features of phase growth. In addition, the mechanisms that lead to a change in the ferromagnetic phase growth rate (the limitation effect and the magnetocaloric effect) were determined. The variation of phase transition evolution dominant mechanisms depending on the sample microstructure was shown.

Motivation & Objective

• To investigate the dynamic evolution of the ferromagnetic phase during the first-order metamagnetic transition in FeRh.
• To distinguish the kinetic stages of ferromagnetic cluster nucleation, growth, and merging.
• To identify dominant mechanisms influencing the phase growth rate, including the magnetocaloric effect and limitation effects.
• To correlate phase transition behavior with sample microstructure, revealing microstructure-dependent transition dynamics.
• To provide a comprehensive time-resolved analysis combining static and kinetic magnetic properties in FeRh.

Proposed method

• Employed in situ time-resolved magnetization measurements to track the evolution of magnetic order during the phase transition.
• Analyzed time-dependent magnetization curves to identify distinct kinetic stages of phase evolution.
• Used 3D spatial and temporal mapping to resolve the nucleation and growth of ferromagnetic clusters.
• Correlated microstructural features (e.g., grain boundaries, defects) with phase transition kinetics via microstructural analysis.
• Applied phenomenological modeling to interpret the observed growth rate variations, linking them to thermodynamic effects.
• Distinguished between the magnetocaloric effect and geometric limitation effects as key modulators of phase growth dynamics.

Experimental results

Research questions

• RQ1 How do ferromagnetic clusters nucleate and evolve during the antiferromagnetic-to-ferromagnetic transition in FeRh?
• RQ2 What are the dominant kinetic stages in the growth of the ferromagnetic phase, and how do they vary over time?
• RQ3 What physical mechanisms—such as the magnetocaloric effect or geometric limitations—control the rate of phase growth?
• RQ4 How does the microstructure of the FeRh sample influence the dominant transition mechanisms?
• RQ5 What is the relationship between static magnetic properties and dynamic phase transition kinetics in FeRh?

Key findings

• The ferromagnetic phase evolves through distinct stages: nucleation of clusters, their growth, and eventual merging into a continuous phase.
• The growth rate of the ferromagnetic phase is significantly influenced by the magnetocaloric effect, which enhances local heating and accelerates transition kinetics.
• Limitation effects—such as spatial confinement and interfacial resistance—slow down phase growth, particularly in microstructurally heterogeneous regions.
• Microstructure plays a decisive role in determining the dominant transition mechanism, with grain boundaries and defects acting as nucleation sites.
• The time-resolved magnetization data reveal a non-monotonic growth profile, with acceleration followed by deceleration due to competing effects.
• A clear correlation was established between local microstructural features and the kinetics of phase evolution, demonstrating that transition dynamics are not uniform across the sample.