Magnetic anisotropy of La2Co7

Kuz’min, M. D.; Skokov, Konstantin P.; Radulov, I.; Schwöbel, C. A.; Foro, Sabine; Donner, W.; Werwiński, Mirosław; Rusz, Ján; Delczeg‐Czirjak, Erna K.; Gutfleisch, Oliver

doi:10.1063/1.4927849

Cited by 18 publications

(9 citation statements)

References 20 publications

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“…The hard-axis magnetization curve does not reach the same maximum value as the easy-axis curve above µ0Ha, due to anisotropy of the magnetic moment. This observed difference of the easy and hard axes magnetization values above the anisotropy field indicates a possible anisotropy of the magnetization, as has been reported for different rare-earth transition-meal systems [92][93][94]. Additionally, the low field region of the hard axis measurements shows non-linear behavior which is due to the formation of twins in the "single-crystals".…”

Section: Single Crystals and Intrinsic Magnetic Propertiessupporting

confidence: 66%

Twins – A weak link in the magnetic hardening of ThMn12-type permanent magnets

et al. 2021

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Nd2Fe14B-type materials exhibit the highest energy product around room temperature and hence dominate the high-performance permanent magnet market. Intensive research efforts aim at alternative material systems containing less critical elements with similar or better magnetic properties. Nd-and Sm-based compounds with a ThMn12-type structure exhibit intrinsic properties comparable or even superior to Nd2Fe14B. However, it has not been possible to achieve technically relevant coercivity and remanent magnetization in ThMn12-based bulk sintered magnets. Using SmFe11Ti as a prototypical representative, we demonstrate that one important reason for the poor performance is the formation of twins inside micro-crystalline grains. The nature of the twins in SmFe11Ti was investigated in twinned "single crystals" and both bulk and thin film poly-crystalline samples, using advanced electron microscopy and atom probe tomography as well as simulations and compared with benchmark Nd2Fe14B. Both micro-twins and nano-twins show a twin orientation of 57±2 • and an enrichment in Sm, which could affect domain wall motion in this 2 material. Micromagnetic simulations indicate that twins act as nucleation centers, representing the magnetically weakest link in the microstructure. The relation between twin formation energies and geometrical features are briefly discussed using molecular dynamic simulations.

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Section: Single Crystals and Intrinsic Magnetic Propertiessupporting

confidence: 66%

Twins – A weak link in the magnetic hardening of ThMn12-type permanent magnets

et al. 2021

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“…In this Letter, we show through precise atomistic computer simulations and Green's function theory calculations for classical spins that the two-ion anisotropy in cubic crystals scales with the reduced magnetization as k(m) ∼ m 2.28 for nearestneighbor coupling, in contrast to the commonly accepted mean-field value of k(m) ∼ m 2 . Notably, in the case of mixed two-ion and single-ion anisotropy, we find that the scaling exponent can radically vary, including reaching negative values as observed in rare-earth-based permanent magnets [6][7][8]. For the technologically relevant, highly anisotropic material L1 0 -FePt, we reproduce its peculiar temperature dependence of k ∼ m 2.1 based on single-ion and two-ion anisotropies of opposite signs.…”

mentioning

confidence: 64%

“…Almost two decades ago, research into magnetic 3d5d intermetallic alloys uncovered a scaling exponent of l = 2.1 in L1 0 -FePt [9], in contrast with the theoretically predicted scaling exponent of l = 3 for uniaxial anisotropy. Rare-earthtransition-metal permanent magnets often exhibit even more complicated behavior with an increase of the anisotropy with temperature [10][11][12][13], corresponding to a negative scaling exponent. Theoretical work attributed the unusual scaling exponent in FePt either to the longitudinal dynamics of the induced Pt moments [14] or to two-ion anisotropy.…”

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confidence: 99%

Temperature scaling of two-ion anisotropy in pure and mixed anisotropy systems

et al. 2020

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Magnetic anisotropy plays an essential role in information technology applications of magnetic materials, providing a means to retain the long-term stability of a magnetic state in the presence of thermal fluctuations. Anisotropy consists of a single-ion contribution stemming from the crystal structure and two-ion terms attributed to the exchange interactions between magnetic atoms. A lack of robust theory crucially limits the understanding of the temperature dependence of the anisotropy in pure two-ion and mixed single-ion and two-ion systems. Here, we use Green's function theory and atomistic Monte Carlo simulations to determine the temperature scaling of the effective anisotropy in ferromagnets in these pure and mixed cases, from saturated to vanishing magnetization. At low temperature, we find that the pure two-ion anisotropy scales with the reduced magnetization as k(m) ∼ m 2.28 , while the mixed scenario describes the diversity of the temperature dependence of the anisotropy observed in real materials. The deviation of the scaling exponent of the mixed anisotropy from previous mean-field results is ascribed to correlated thermal spin fluctuations, and its value determined here is expected to considerably contribute to the understanding and the control of the thermal properties of magnetic materials.

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“…This and the inclusion of the TM contribution to the MAE are clearly advantages of the total-energy calculations. However, in order to obtain quantitatively accurate values for K 1 and H a dense k-meshes of several thousands of k-points are needed for the Brillouin-zone integrals 27 28 . This make total-energy calculations for HTS rather disadvantageous.…”

Section: Resultsmentioning

confidence: 99%

Theoretical screening of intermetallic ThMn12-type phases for new hard-magnetic compounds with low rare earth content

Körner

Krugel

Elsässer

2016

Sci Rep

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We report on theoretical investigations of intermetallic phases derived from the ThMn12-type crystal structure. Our computational high-throughput screening (HTS) approach is extended to an estimation of the anisotropy constant K1, the anisotropy field Ha and the energy product (BH)max. The calculation of K1 is fast since it is based on the crystal field parameters and avoids expensive total-energy calculations with many k-points. Thus the HTS approach allows a very efficient search for hard-magnetic materials for which the magnetization M and the coercive field Hc connected to Ha represent the key quantities. Besides for NdFe12N which has the highest magnetization we report HTS results for several intermetallic phases based on Cerium which are interesting as alternative hard-magnetic phases because Cerium is a less ressource-critical element than Neodymium.

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Magnetic anisotropy of La2Co7

Cited by 18 publications

References 20 publications

Twins – A weak link in the magnetic hardening of ThMn12-type permanent magnets

Twins – A weak link in the magnetic hardening of ThMn12-type permanent magnets

Temperature scaling of two-ion anisotropy in pure and mixed anisotropy systems

Theoretical screening of intermetallic ThMn12-type phases for new hard-magnetic compounds with low rare earth content

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