Mössbauer Study of Hyperfine Fields and Isomer Shifts in the Fe-Rh Alloys

Shirane, G.; Chen, C. W.; Flinn, P. A.; Nathans, R.

doi:10.1103/physrev.131.183

Cited by 190 publications

(109 citation statements)

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“…The spectra can in this case be modeled with a first-neighbor ratio N Rh =N Fe equal to 4=3 and a distance ratio R Rh =R Fe equal to ffiffiffi 3 p =2, as expected for the B2 phase. The unit cell volume ð2:98 AÞ 3 coincides with that of bulk B2 FeRh [8]. The number of C atoms neighboring the emitting Fe is reduced upon annealing, in agreement with XMCD measurements.…”

supporting

confidence: 69%

“…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].…”

mentioning

confidence: 99%

“…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].…”

mentioning

confidence: 99%

“…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].…”

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confidence: 99%

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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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confidence: 99%

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confidence: 99%

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Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

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“…The antiferromagnetic phase is of G type with 3.3 B per Fe atom and no Rh moment. 6,7 A significant magnetoresistance of 90% was found for bulk FeRh at room temperature and up to 1700% at 4.2 K for polycrystalline FeRh. 8 The transition may be affected and hence controlled by many factors, including the applied magnetic field, 9 ion-irradiation, 10 stress state, 11 and the sample microstructural scale.…”

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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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Creating a Ferromagnetic Ground State with T_c Above Room Temperature in a Paramagnetic Alloy through Non‐Equilibrium Nanostructuring

Fortunato

Sarkar

et al. 2022

Advanced Materials

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Materials with strong magnetostructural coupling have complex energy landscapes featuring multiple local ground states, thus making it possible to switch among distinct magnetic‐electronic properties. However, these energy minima are rarely accessible by a mere application of an external stimuli to the system in equilibrium state. A ferromagnetic ground state, with Tc above room temperature, can be created in an initially paramagnetic alloy by nonequilibrium nanostructuring. By a dealloying process, bulk chemically disordered FeRh alloys are transformed into a nanoporous structure with the topology of a few nanometer‐sized ligaments and nodes. Magnetometry and Mössbauer spectroscopy reveal the coexistence of two magnetic ground states, a conventional low‐temperature spin‐glass and a hitherto‐unknown robust ferromagnetic phase. The emergence of the ferromagnetic phase is validated by density functional theory calculations showing that local tetragonal distortion induced by surface stress favors ferromagnetic ordering. The study provides a means for reaching conventionally inaccessible magnetic states, resulting in a complete on/off ferromagnetic–paramagnetic switching over a broad temperature range.

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Mössbauer Study of Hyperfine Fields and Isomer Shifts in the Fe-Rh Alloys

Cited by 190 publications

References 13 publications

Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

Ferromagnetism at the interfaces of antiferromagnetic FeRh epilayers

Creating a Ferromagnetic Ground State with T_c Above Room Temperature in a Paramagnetic Alloy through Non‐Equilibrium Nanostructuring

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Mössbauer Study of Hyperfine Fields and Isomer Shifts in the Fe-Rh Alloys

Cited by 190 publications

References 13 publications

Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

Ferromagnetism at the interfaces of antiferromagnetic FeRh epilayers

Creating a Ferromagnetic Ground State with Tc Above Room Temperature in a Paramagnetic Alloy through Non‐Equilibrium Nanostructuring

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Creating a Ferromagnetic Ground State with T_c Above Room Temperature in a Paramagnetic Alloy through Non‐Equilibrium Nanostructuring