<p>FeRh undergoes a first-order antiferromagnetic–ferromagnetic (AFM–FM) transition near room temperature that strongly affects electronic transport. Bulk FeRh shows large but localized Thomson responses near the thermally induced transition. Here, we show that this behavior is tunable in thin films. We measure the thermomagnetic responses of near-equimolar FeRh films (20–80 nm) grown on <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$\hbox {Al}_2$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>Al</mtext> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation> <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$\hbox {O}_3$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>O</mtext> <mn>3</mn> </msub> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\hbox {SiO}_2$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>SiO</mtext> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation>/Si, and MgO. For films grown on the same substrate, increasing thickness reduces strain and sharpens the AFM–FM transition, yielding a correspondingly sharper Thomson response. Thicker films reach peaks exceeding <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$-250$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>-</mo> <mn>250</mn> </mrow> </math></EquationSource> </InlineEquation> <InlineEquation ID="IEq5"> <EquationSource Format="TEX">$\mu$</EquationSource> <EquationSource Format="MATHML"><math> <mi>μ</mi> </math></EquationSource> </InlineEquation>V <InlineEquation ID="IEq6"> <EquationSource Format="TEX">$\hbox {K}^{-1}$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mtext>K</mtext> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </math></EquationSource> </InlineEquation> over narrow temperature ranges, whereas thinner films display smaller peaks spanning up to <InlineEquation ID="IEq7"> <EquationSource Format="TEX">$\sim$</EquationSource> <EquationSource Format="MATHML"><math> <mo>∼</mo> </math></EquationSource> </InlineEquation>100 K. Changing the substrate alters crystallinity, microstructure, and strain, leading to pronounced differences in the baseline Seebeck coefficient in both phases. These results demonstrate that strain and microstructure enable engineering the magnitude and temperature span of the Thomson effect in FeRh thin films.</p> Graphical Abstract <p></p>

Substrate-dependent magneto-thermoelectric properties in FeRh thin films during antiferromagnetic–ferromagnetic phase transition

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2026年5月4日

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Md Sabbir Akhanda,
Sree Sourav Das,
Megan Lenox,
Benjamin Aronson,
Shelby Fields,
Steven P. Bennett,
Jae Won Choi,
Jung-Min Cho,
Bellave Shivaram,
Sang-Kwon Lee,
Jon F. Ihlefeld,
Mona Zebarjadi

摘要

FeRh undergoes a first-order antiferromagnetic–ferromagnetic (AFM–FM) transition near room temperature that strongly affects electronic transport. Bulk FeRh shows large but localized Thomson responses near the thermally induced transition. Here, we show that this behavior is tunable in thin films. We measure the thermomagnetic responses of near-equimolar FeRh films (20–80 nm) grown on $\hbox {Al}_2$ ${Al}_{2}$ $\hbox {O}_3$ $O_{3}$ , $\hbox {SiO}_2$ ${SiO}_{2}$ /Si, and MgO. For films grown on the same substrate, increasing thickness reduces strain and sharpens the AFM–FM transition, yielding a correspondingly sharper Thomson response. Thicker films reach peaks exceeding $-250$ $- 250$ $\mu$ $μ$ V $\hbox {K}^{-1}$ $K^{- 1}$ over narrow temperature ranges, whereas thinner films display smaller peaks spanning up to $\sim$ $\sim$ 100 K. Changing the substrate alters crystallinity, microstructure, and strain, leading to pronounced differences in the baseline Seebeck coefficient in both phases. These results demonstrate that strain and microstructure enable engineering the magnitude and temperature span of the Thomson effect in FeRh thin films.

Graphical Abstract