Magnetic order multilayering in FeRh thin films by He-Ion irradiation

Bennett, Steven; Herklotz, Andreas; Cress, Cory D.; Ievlev, Anton V.; Rouleau, Christopher M.; Mazin, I. I.; Lauter, Valeria

doi:10.1080/21663831.2017.1402098

Cited by 38 publications

(44 citation statements)

References 38 publications

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“…[ 32 ] Erasure by cooling also shows that the FM domains are due to the bistability of both AF phases at room temperature and not a reduced transition temperature from local damage to the atomic structure. [ 33 ]…”

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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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: 99%

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

et al. 2020

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“…While bulk FeRh is prohibitively expensive, Fe-Rh may find use in caloric thin-film 19,21,36,44,[62][63][64][65][66][67][68][69][70] and nanoscale devices. 43,59,[71][72][73][74][75][76][77][78][79] Nonetheless, and notably here, it mainly serves as a well-studied but suitably complex system to test methods for reliability in thermodynamic assessments and prediction of caloric properties, specifically because it exhibits instabilities from anharmonic atomic motion, which affects caloric behavior.…”

Section: Introductionmentioning

confidence: 99%

Reliable thermodynamic estimators for screening caloric materials

Zarkevich

Johnson

2019

Journal of Alloys and Compounds

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Reversible, diffusionless, first-order solid-solid phase transitions accompanied by caloric effects are critical for applications in the solid-state cooling and heat-pumping devices. Accelerated discovery of caloric materials requires reliable but faster estimators for predictions and high-throughput screening of system-specific dominant caloric contributions. We assess reliability of the computational methods that provide thermodynamic properties in relevant solid phases at or near a phase transition. We test the methods using the well-studied B2 FeRh alloy as a "fruit fly" in such a materials genome discovery, as it exhibits a metamagnetic transition which generates multicaloric (magneto-, elasto-, and baro-caloric) responses. For lattice entropy contributions, we find that the commonly-used linear-response and smalldisplacement phonon methods are invalid near instabilities that arise from the anharmonicity of atomic potentials, and we offer a more reliable and precise method for calculating lattice entropy at a fixed temperature. Then, we apply a set of reliable methods and estimators to the metamagnetic transition in FeRh (predicted 346 ± 12 K, observed 353 ± 1 K) and calculate the associated caloric properties, such as isothermal entropy and isentropic temperature changes.

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“…High-coercivity permanent magnets are indisputably one of the critical materials indispensible for modern technologies in which electrical energy is converted to motion with a high efficiency or vice versa [1][2][3][4]. Among all the available permanent magnets, nowadays Nd-Fe-B (neodymium-iron-boron) is the most powerful and commercially important magnet.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic exchange in Nd–Fe–B permanent magnets

Gong

Evans

Gutfleisch

et al. 2019

Materials Research Letters

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The exchange is critical for designing high-performance Nd-Fe-B permanent magnets. Here we demonstrate through multiscale simulations that the exchange in Nd-Fe-B magnets, including bulk exchange stiffness (A e) in Nd 2 Fe 14 B phase and interface exchange coupling strength (J int) between Nd 2 Fe 14 B and grain boundary (GB), is strongly anisotropic. A e is larger along crystallographic a/b axis than along c axis. Even when the GB Fe x Nd 1−x has the same composition, J int for (100) interface is much higher than that for (001) interface. The discovered anisotropic exchange is shown to have profound influence on the coercivity. These findings enable more freedom in designing Nd-Fe-B magnets by tuning exchange. IMPACT STATEMENT Bulk exchange stiffness in Nd 2 Fe 14 B and interface exchange coupling strength between Nd 2 Fe 14 B and grain boundary are found strongly anisotropic, which have profound influence on the coercivity of Nd-Fe-B magnets.

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Magnetic order multilayering in FeRh thin films by He-Ion irradiation

Cited by 38 publications

References 38 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

Reliable thermodynamic estimators for screening caloric materials

Anisotropic exchange in Nd–Fe–B permanent magnets

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