Ferromagnetic stabilization of ordered B2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">FeRh</mml:mi></mml:math>thin films

Lounis, Samir; Benakki, M.; Demangeat, C.

doi:10.1103/physrevb.67.094432

Cited by 35 publications

(35 citation statements)

References 34 publications

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“…Subsequent work argued that in analogy to Fe, gradient corrected functionals (GGA) are required for the correct description of FeRh 8 . It was shown that while LDA and GGA functionals predict similar structures, the magnetic moments on Fe in the AFM phase are significantly larger and in better agreement with experiment using GGA 9 . Later work showed that close to the transition volume, the Fe moments are unstable with respect to canting when treated at the LDA level whereas a semi-local GGA functional stabilises the collinear FM phase 10 .…”

Section: Introductionmentioning

confidence: 61%

Strain-induced structural instability in FeRh

et al. 2016

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We perform density functional calculations to investigate the structure of the inter-metallic alloy FeRh under epitaxial strain. Bulk FeRh exhibits a metamagnetic transition from a low-temperature antiferromagnetic (AFM) phase to a ferromagnetic (FM) phase at 350K, and its strain dependence is of interest for tuning the transition temperature to the room-temperature operating conditions of typical memory devices. We find an unusually strong dependence of the structural energetics on the choice of exchange-correlation functional, with the usual local density approximation (LDA) yielding the wrong ground-state structure, and generalized gradient (GGA) extensions being in better agreement with the bulk experimental structure. Using the GGA we show the existence of a metastable face-centered-cubic (fcc)-like AFM structure that is reached from the ground state body-centered-cubic (bcc) AFM structure by following the epitaxial Bain path. We predict that this metastable fcc-like structure has a significantly higher conductivity than the bcc AFM phase. We show that the behavior is well described using non-linear elasticity theory, which captures the softening and eventual sign change of the orthorhombic shear modulus under compressive strain, consistent with this structural instability. Finally, we predict the existence of an additional unitcell-doubling lattice instability, which should be observable at low temperature.

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Section: Introductionmentioning

confidence: 61%

Strain-induced structural instability in FeRh

et al. 2016

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“…Theoretical studies have highlighted the importance of a Rh moment to the stability of the FM phase. Ab initio studies 15,31 for Rh-terminated surfaces indicate a magnetic surface reconstruction favoring a p͑1 ϫ 1͒ FM arrangement stable up to nine layers. The termination leads to an increased density of states on the Rh d electrons leading to a moment on the Rh site.…”

Section: Discussionmentioning

confidence: 99%

“…14 Band-structure calculations by Lounis et al 15 have shown that there is a clear correlation between the thickness of the FeRh thin films and the stability of the FM/AF configuration with ferromagnetism being stabilized for nine atomic layers for a Rh-terminated system. In our previous study, x-ray magnetic circular dichroism ͑XMCD͒ showed that FeRh has a finite magnetic moment close to the top surface at room temperature 16 and more recently grazing incident x-ray diffraction shows that a near-surface relaxation occurs at the top interface which could contribute to the stability of the roomtemperature FM top surface.…”

Section: Introductionmentioning

confidence: 99%

Ferromagnetism at the interfaces of antiferromagnetic FeRh epilayers

et al. 2010

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. The nanoscale magnetic structure of FeRh epilayers has been studied by polarized neutron reflectometry. Epitaxial films with a nominal thickness of 500 Å were grown on MgO ͑001͒ substrates via molecular-beam epitaxy and capped with 20 Å of MgO. The FeRh films show a clear transition from the antiferromagnetic ͑AF͒ state to the ferromagnetic ͑FM͒ state with increasing temperature. Surprisingly the films possess a FM moment even at a temperature 80 K below the AF-FM transition temperature of the film. We have quantified the magnitude and spatial extent of this FM moment, which is confined to within ϳ60-80 Å of the FeRh near the top and bottom interfaces. These interfacial FM layers account for the unusual effects previously observed in films with thickness Ͻ100 Å. Given the delicate energy balance between the AF and FM ground states we suggest a metastable FM state resides near to the interface within an AF matrix. The length scale over which the FM region resides is consistent with the strained regions of the film.

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“…Strained thin films [13,14] showed traces of a FM phase down to 300 K, while ab initio calculations predicted FM down to 0 K for a Rh-terminated 9 ML FeRh(001) film [15] and for 8-atom FeRh clusters [16]. Indeed, since nanosized crystals may present significantly different interatomic distances and unit cell distortions with respect to bulk [17,18], a fundamentally modified magnetic phase diagram can be expected for FeRh nanocrystals.…”

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Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

et al. 2013

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In sharp contrast to previous studies on FeRh bulk, thin films, and nanoparticles, we report the persistence of ferromagnetic order down to 3 K for size-selected 3.3 nm diameter nanocrystals embedded into an amorphous carbon matrix. The annealed nanoparticles have a B2 structure with alternating atomic Fe and Rh layers. X-ray magnetic dichroism and superconducting quantum interference device measurements demonstrate ferromagnetic alignment of the Fe and Rh magnetic moments of 3 and 1 B , respectively. The ferromagnetic order is ascribed to the finite-size induced structural relaxation observed in extended x-ray absorption spectroscopy. DOI: 10.1103/PhysRevLett.110.087207 PACS numbers: 75.30.Kz, 75.75.Cd, 81.07.Bc Iron-rhodium alloys exhibit competing ferromagnetic (FM) and antiferromagnetic (AFM) phases with transition temperatures close to ambient for nearly equiatomic composition and body-centered-cubic (bcc) CsCl-like B2 structure. The competition between the two magnetic orders of FeRh holds great potential in spintronics and heat assisted magnetic recording [1,2]. Moreover, the peculiar bulk FeRh magnetic phase diagram enables its use as active material in heat pumps and refrigerators [3][4][5].At ambient conditions, bulk B2 FeRh is a G-type AFM with a total magnetic moment on the iron atoms of 3:3 B and no appreciable moment on the rhodium atoms [6][7][8]. Above the transition temperature of 370 K, the atomic moments of Fe and Rh are ferromagnetically aligned and take on total values of 3.2 and 0:9 B , respectively [6][7][8]. While it has long been known that the bcc unit cell volume expands by % 1% upon transforming to FM order [9], recent experiments suggest that distortions of the bcc structure may occur [10]. Given the itinerant character of the 3d electrons, the coupling between crystallographic and magnetic order in this system is both rich and very delicate as demonstrated by the theoretical challenge to model the system [11], as well as by recent pump-probe experiments focusing on ultrafast magnetization control [12].Finite-size systems of this alloy have received particular attention by their potential to stabilize the FM phase at room temperature and below. Strained thin films [13,14] showed traces of a FM phase down to 300 K, while ab initio calculations predicted FM down to 0 K for a Rh-terminated 9 ML FeRh(001) film [15] and for 8-atom FeRh clusters [16]. Indeed, since nanosized crystals may present significantly different interatomic distances and unit cell distortions with respect to bulk [17,18], a fundamentally modified magnetic phase diagram can be expected for FeRh nanocrystals. However, the first experiments on chemically synthesized FeRh nanoparticles (NPs) failed to evidence low temperature stability of the FM phase. Most notably, they raised important questions, such as partial B2 ordering, elemental segregation, and coalescence upon annealing [19][20][21].In this Letter, we demonstrate the persistence of FM order down to below 3 K in size-selected FeRh nanocrystals with a mean d...

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Ferromagnetic stabilization of ordered B2FeRhthin films

Cited by 35 publications

References 34 publications

Strain-induced structural instability in FeRh

Strain-induced structural instability in FeRh

Ferromagnetism at the interfaces of antiferromagnetic FeRh epilayers

Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

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