Laser-driven formation of transient local ferromagnetism in FeRh thin films

Ünal, A. A.; Parabas, Adem; Arora, Anu; Ehrler, Jonathan; Barton, Christopher; València, S.; Bali, Rantej; Thomson, Thomas; Yıldız, F.; Kronast, Florian

doi:10.1016/j.ultramic.2017.03.024

Cited by 11 publications

(8 citation statements)

References 21 publications

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“…Time scales for nucleation and reorientation vary between 20–50 and 50–100 ps, respectively, depending on film composition and thickness. [ 35 ] Our films reach peak temperature 20 ps after the pulse arrival as shown in Section S5, Supporting Information. We therefore estimate the writing time in our samples to be between 100 and 200 ps.…”

Section: Figurementioning

confidence: 89%

“…Nevertheless, the image obtained after cooling shows that the FM patterns are still erasable by cooling and the higher fluence does not damage the sample. Previous pump‐probe measurements of the laser‐induced phase transition using femtosecond pulses [ 28,29,34,35 ] indicate that ferromagnetic domains first nucleate in different orientations and then orient together toward the applied magnetic field. Time scales for nucleation and reorientation vary between 20–50 and 50–100 ps, respectively, depending on film composition and thickness.…”

Section: Figurementioning

confidence: 99%

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Local Photothermal Control of Phase Transitions for On‐Demand Room‐Temperature Rewritable Magnetic Patterning

et al. 2020

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The ability to make controlled patterns of magnetic structures within a nonmagnetic background is essential for several types of existing and proposed technologies. Such patterns provide the foundation of magnetic memory and logic devices 1 , allow the creation of artificial spinice lattices 2,3 and enable the study of magnon propagation 4 . Here, we report a novel approach for magnetic patterning that allows repeated creation and erasure of arbitrary shapes of thin-film ferromagnetic structures. This strategy is enabled by epitaxial Fe 0.52 Rh 0.48 thin films designed so that both ferromagnetic and antiferromagnetic phases are bistable at room temperature. Starting with the film in a uniform antiferromagnetic state, we demonstrate the ability to write arbitrary patterns of the ferromagnetic phase by local heating with a focused laser. If desired, the results can then be erased by cooling with a thermoelectric cooler and the material repeatedly repatterned.Intermetallic Fe 1-x Rh x (B2, P m3m) exhibits a hysteretic antiferromagnetic/ferromagnetic transformation which has been harnessed to produce composite multiferroics exhibiting record-breaking magnetoelectric coupling coefficients 5 , magnetocaloric refrigerators with competitive cooling capabilities 6 and novel memories based on antiferromagnetic order 7 . In this study, we design epitaxial Fe 1-x Rh x films so that both ferromagnetic and antiferromagnetic states are simultaneously bistable at room temperature. We engineer the width of the thermal hysteresis to be sufficiently narrow to enable efficient controllability, but also wide enough to robustly withstand thermal perturbations. Moderate heating by a focused laser is used to locally drive antiferromagnetic regions controllably to the ferromagnetic phase, demonstrating the patterning of arbitrary magnetic features on the submicron scale. These findings present opportunities for writing and erasing high-fidelity magnetically active nanostructures that are of interest for magnonic crystals 8 , artificial spin-ice lattices 9 and memory 10 and logic devices 11 . FIG. 1.Fully-dense phase-pure untwinned epitaxial B2 Fe0.52Rh0.48/MgO(001) layers grown via molecular-beam epitaxy. a, RBS spectrum; labeled iron and rhodium spectral features correspond to a magnetically bistable rhodium fraction of 0.48. b, BF-TEM image of the entire film cross section together with c, a corresponding SAED pattern. Note the weaker film and more intense substrate reflections. d, XRD θ-2θ scan; film (violet) and substrate (orange) reflections are indexed. e, XRD ω-rocking scan about the 001 film peak.Fe 1-x Rh x films are grown epitaxially on singlecrystalline (001)-oriented MgO substrates using molecular-beam epitaxy. The fraction x of rhodium in the film is carefully tuned to 0.48, where the hysteretic antiferromagnet/ferromagnet phase transitions are centered near room temperature. Film compositions are confirmed via Rutherford backscattering spectrometry (RBS) measurements (Fig. 1a) using the areal ratio of corresponding iron and...

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Section: Figurementioning

confidence: 89%

Section: Figurementioning

confidence: 99%

Local Photothermal Control of Phase Transitions for On‐Demand Room‐Temperature Rewritable Magnetic Patterning

et al. 2020

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“…These temperatures are close to or coincide with the reverse martensitic transformation starting temperatures A s (B2-TiNi) ~ 100 °C, A s (B2-NiAl) ~ 180 °C, A s (B2-CdAu) = 67 °C. The reversible α l ʹ ↔ αʺ transition in B2-FeRh possesses all the characteristics of a martensitic transformation (α l ′-austenite, αʺ-martensite), because it can pass at high speeds 52,53 , has isotropic volume changes at the transition 1 , can be www.nature.com/scientificreports/ induced by the application of stress 19,20,24,25,[37][38][39][40] and magnetic field 1,9,10 , has martensitic instabilities 36,54 and the α l ʹ and αʺ lattices have a cube-on-cube orientation relationship. According to the phase diagram, the transition α l ʹ ↔ αʺ has a minimum temperature T k ~ 100 °C among other structural transformations in the Fe-Rh system.…”

Section: Discussionmentioning

confidence: 99%

Solid-state synthesis, magnetic and structural properties of interfacial B2-FeRh(001) layers in Rh/Fe(001) films

Myagkov

Ivanenko

Быкова

et al. 2020

Sci Rep

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Here we first report results of the start of the solid-state reaction at the Rh/Fe(001) interface and the structural and magnetic phase transformations in 52Rh/48Fe(001), 45Rh/55Fe(001), 68Rh/32Fe(001) bilayers from room temperature to 800 °C. For all bilayers the non-magnetic nanocrystalline phase with a B2 structure (nfm-B2) is the first phase that is formed on the Rh/Fe(001) interface near 100 °C. Above 300 °C, without changing the nanocrystalline B2 structure, the phase grows into the low-magnetization modification α l ʹ (M S l ~ 825 emu/cm 3) of the ferromagnetic α ʹ phase which has a reversible α l ʹ ↔ αʺ transition. After annealing 52Rh/48Fe(001) bilayers above 600 °C the α l ʹ phase increases in grain size and either develops into α h ʹ with high magnetization (M S h ~ 1,220 emu/cm 3) or remains in the α l ʹ phase. In contrast to α l ʹ, the α h ʹ ↔ αʺ transition in the α h ʹ films is completely suppressed. When the annealing temperature of the 45Rh/55Fe(001) samples is increased from 450 to 800 °C the low-magnetization nanocrystalline α l ʹ films develop into high crystalline perfection epitaxial α h ʹ(001) layers, which have a high magnetization of ~ 1,275 emu/cm 3. α h ʹ(001) films do not undergo a transition to an antiferromagnetic αʺ phase. In 68Rh/32Fe(001) samples above 500 °C non-magnetic epitaxial γ(001) layers grow on the Fe(001) interface as a result of the solid-state reaction between the epitaxial α l ʹ(001) and polycrystalline Rh films. Our results demonstrate not only the complex nature of chemical interactions at the low-temperature synthesis of the nfm-B2 and α l ʹ phases in Rh/Fe(001) bilayers, but also establish their continuous link with chemical mechanisms underlying reversible α l ʹ ↔ αʺ transitions. An intriguing feature of the equilibrium diagram of the Fe-Rh system is the existence of the low-temperature transition at T K αʺ→αʹ ~ 100 °C between antiferromagnetic (AFM) αʺ and ferromagnetic (FM) αʹ phases in a narrow (0.48 < x Rh < 056) concentration interval in chemically ordered B2-FeRh alloys 1. This transition is accompanied by an isotropic volume expansion of ~ 1% of the B2-FeRh unit cell, which not only radically changes the magnetic properties, but also changes the entropy 2,3 and resistivity 4. The magnetostructural αʺ → αʹ (AFM-FM) transition gives existence to the giant magnetostriction 5 large magnetoresistance 6,7 and magnetocaloric effects 8 in B2-FeRh alloys. Numerous studies of bulk samples indicate that the starting temperature T K αʺ→αʹ and characteristics of the αʺ → αʹ transition may be modified by variations the magnetic field 9,10 , microstructure 11 , thermal treatment 12 , energetic ion irradiation 13 , stress 14 and hydrostatic pressure 15-17 and can also be tuned over a wide temperature range (100-600 K) by chemical substitution 9,18. Although bulk B2-FeRh samples exhibit a sharp transition with a small thermal hysteresis, thin films and nanoparticles often have an incomplete and broad asymmetrical hysteresis AFM-FM transition 1,19-34. The starting transition...

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“…The most well-developed of these is TR magneto-optical Kerr effect (MOKE) 5 , showing that the Kerr signal from the FM phase emerges within 100 ps 26 following excitation with a fs laser pulse. Further investigations using TR photoemission electron microscopy (PEEM) show that the FM domains are established only after 200–500 ps 27 . This delay is associated with the asymmetric transition behaviour of the material 28 so that AF → FM is not equivalent to FM → AF under time reversal symmetry.…”

Section: Introductionmentioning

confidence: 99%

Determination of sub-ps lattice dynamics in FeRh thin films

Grimes

Ueda

Ozerov

et al. 2022

Sci Rep

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Understanding the ultrashort time scale structural dynamics of the FeRh metamagnetic phase transition is a key element in developing a complete explanation of the mechanism driving the evolution from an antiferromagnetic to ferromagnetic state. Using an X-ray free electron laser we determine, with sub-ps time resolution, the time evolution of the (–101) lattice diffraction peak following excitation using a 35 fs laser pulse. The dynamics at higher laser fluence indicates the existence of a transient lattice state distinct from the high temperature ferromagnetic phase. By extracting the lattice temperature and comparing it with values obtained in a quasi-static diffraction measurement, we estimate the electron–phonon coupling in FeRh thin films as a function of laser excitation fluence. A model is presented which demonstrates that the transient state is paramagnetic and can be reached by a subset of the phonon bands. A complete description of the FeRh structural dynamics requires consideration of coupling strength variation across the phonon frequencies.

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Laser-driven formation of transient local ferromagnetism in FeRh thin films

Cited by 11 publications

References 21 publications

Local Photothermal Control of Phase Transitions for On‐Demand Room‐Temperature Rewritable Magnetic Patterning

Local Photothermal Control of Phase Transitions for On‐Demand Room‐Temperature Rewritable Magnetic Patterning

Solid-state synthesis, magnetic and structural properties of interfacial B2-FeRh(001) layers in Rh/Fe(001) films

Determination of sub-ps lattice dynamics in FeRh thin films

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