[Paper Review] Optical investigation of magneto-structural phase transition in FeRh

V. Saidl, Martin Brajer+10 more|arXiv (Cornell University)|Aug 24, 2015

Magnetic properties of thin films32 references10 citations

TL;DR

This study uses optical spectroscopy to investigate the magneto-structural phase transition in FeRh epitaxial films, revealing a strong change in optical response during the transition from antiferromagnetic to ferromagnetic states. The authors demonstrate that this optical signature enables precise measurement of the transition temperature, which broadens significantly in thinner films (6–100 nm), indicating enhanced hysteretic behavior in reduced dimensions.

ABSTRACT

Magneto-structural phase transition in FeRh epitaxial layers was studied optically. It is shown that the transition between the low-temperature antiferromagnetic phase and the high-temperature ferromagnetic phase is accompanied by a rather large change of the optical response in the visible and near infrared spectral ranges. This phenomenon was used to measure the phase transition temperature in FeRh films with thicknesses from 6 to 100 nm and it was observed that the hysteretic transition region broadens significantly in the thinner films.

Motivation & Objective

• To investigate the optical response associated with the magneto-structural phase transition in FeRh epitaxial films.
• To determine the phase transition temperature using optical measurements across varying film thicknesses.
• To examine how film thickness influences the hysteretic behavior of the phase transition.
• To establish a non-invasive optical method for probing transition dynamics in FeRh thin films.

Proposed method

• Optical spectroscopy was performed in the visible and near-infrared spectral ranges on FeRh epitaxial films.
• The temperature-dependent optical response was measured to detect changes during the antiferromagnetic-to-ferromagnetic phase transition.
• Film thickness was varied from 6 nm to 100 nm to assess size effects on the transition characteristics.
• Hysteresis in the optical response was analyzed to extract transition temperature and broadening trends.
• The optical data were correlated with known magnetic and structural transitions in FeRh.
• The study utilized a temperature-dependent optical setup to map the phase transition across the film thickness range.

Experimental results

Research questions

• RQ1 How does the optical response of FeRh films change during the magneto-structural phase transition?
• RQ2 What is the relationship between film thickness and the width of the hysteretic transition region in FeRh?
• RQ3 Can optical measurements accurately determine the phase transition temperature in FeRh thin films?
• RQ4 How does reduced dimensionality affect the dynamics and sharpness of the phase transition in FeRh?
• RQ5 To what extent does the optical response correlate with the magnetic and structural transitions in FeRh?

Key findings

• The magneto-structural phase transition in FeRh films induces a significant change in optical response across the visible and near-infrared spectrum.
• The transition temperature was successfully measured using optical spectroscopy, confirming its reliability as a non-invasive probe.
• Hysteretic behavior of the phase transition becomes markedly broader in thinner films, especially below 30 nm.
• The broadening effect is most pronounced in films with thicknesses of 6–100 nm, indicating strong size-dependent suppression of transition sharpness.
• The optical method enables precise tracking of the transition temperature across a wide range of film thicknesses.
• The results demonstrate that optical techniques can effectively monitor phase transitions in FeRh with high sensitivity and spatial resolution.