An evaluation of the R—T spin coupling parameter in the rare earth–transition metal intermetallics

Duc, Nguyen Huu

doi:10.1002/pssb.2221640223

Cited by 35 publications

(11 citation statements)

References 17 publications

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“…To estimate the 3 d -3 d and 3 d -4 f exchange interactions in Gd 0.4 Tb 0.6 (Co 1−x Ni x ) 2 compounds, we considered its magnetic structure as consisting of two magnetic sublattices formed by R(Gd/Tb) and T(Co/Ni) moments. We performed the estimation by applying the approach described in detail in [ 6 , 24 , 25 ]. In the evaluation, we used the M ( T ) dependence under the magnetic field of 5 T, which was high enough to avoid the influence of domain effects and achieve a relatively high saturation (black curves in Figure 7 ).…”

Section: Resultsmentioning

confidence: 99%

Effect of Ni Substitution on the Structural, Magnetic, and Electronic Structure Properties of Gd0.4Tb0.6(Co1−xNix)2 Compounds

Sikora

Bajorek

Chrobak

et al. 2022

IJMS

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The comprehensive research of magnetic and electronic structure properties of the new class of Gd0.4Tb0.6(Co1−xNix)2 compounds, crystallizing in the cubic Laves phase (C15), is reported. The magnetic study was completed with electrical resistivity and electronic structure investigations. The analysis of Arrott plots supplemented by a study of temperature dependency of Landau coefficients revealed that all compounds undergo a magnetic phase transition of the second type. Based on magnetic isotherms, magnetic entropy change (ΔSM) was determined for many values of the magnetic field change (μ0H), which varied from 0.1 to 7 T. For each compound, the ΔSM had a maximum around the Curie temperature. Both values of the |ΔSMmax| and relative cooling power RCP parameters increased with increasing nickel content. It is shown that structural disorder upon Co/Ni substitution influences some magnetic parameters. The magnetic moment values of Co atoms determined from different methods are quantitatively consistent. From the M(T) dependency, the exchange integrals JRR, JRT, and JTT between rare-earths (R) and transition metal (T) moments were evaluated within the mean-field theory (MFT) approach. The experimental study of the electronic structure performed with the use of the X-ray photoelectron spectroscopy (XPS) was completed by calculations using the full-potential linearized augmented plane waves (FP-LAPW) method based on the density functional theory (DFT). The calculations explained experimentally observed changes in the XPS valence band spectra upon the Ni/Co substitution.

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Section: Resultsmentioning

confidence: 99%

Effect of Ni Substitution on the Structural, Magnetic, and Electronic Structure Properties of Gd0.4Tb0.6(Co1−xNix)2 Compounds

Sikora

Bajorek

Chrobak

et al. 2022

IJMS

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“…In the MFT approximation, the M R and M T magnetizations can be described as follows [9,[31][32][33]:…”

Section: Mft Analysismentioning

confidence: 99%

“…Because the R sublattice consists of two kinds of rare-earth atoms (described by the Brillouin functions with different ground states) the presented analysis refers to an average value of R magnetic moment. Assuming that the average coordination numbers of R-R (Z RR ), R-Co (Z RCo ), Co-R (Z CoR ), and Co-Co (Z CoCo ) are equal: 4, 12, 6, and 6, respectively[33], we have obtained the following values of exchange coupling integrals: J RR = 1.9 × 10 −23 J, J RCo = −1.17 × 10 −22 J and J CoCo = 3.59 × 10 −22 J.Materials 2020, 13, x FOR PEER REVIEW 8 of 14…”

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confidence: 99%

Magnetic Properties and the Electronic Structure of the Gd0.4Tb0.6Co2 Compound

et al. 2020

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We report on the comprehensive experimental and theoretical studies of magnetic and electronic structural properties of the Gd0.4Tb0.6Co2 compound crystallization in the cubic Laves phase (C15). We present new results and compare them to those reported earlier. The magnetic study was completed with electronic structure investigations. Based on magnetic isotherms, magnetic entropy change (ΔSM) was determined for many values of the magnetic field change (Δμ0H), which varied from 0.1 to 7 T. In each case, the ΔSM had a maximum around room temperature. The analysis of Arrott plots supplemented by a study of temperature dependency of Landau coefficients revealed that the compound undergoes a magnetic phase transition of the second type. From the M(T) dependency, the exchange integrals between rare-earth R-R (JRR), R-Co (JRCo), and Co-Co (JCoCo) atoms were evaluated within the mean-field theory approach. The electronic structure was determined using the X-ray photoelectron spectroscopy (XPS) method as well as by calculations using the density functional theory (DFT) based Full Potential Linearized Augmented Plane Waves (FP-LAPW) method. The comparison of results of ab initio calculations with the experimental data indicates that near TC the XPS spectrum collects excitations of electrons from Co3d states with different values of exchange splitting. The values of the magnetic moment on Co atoms determined from magnetic measurements, estimated from the XPS spectra, and results from ab initio calculations are quantitatively consistent.

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“…An indirect method used to evaluate the value fo A,, is to compare the magnetic ordering temperature of isostructural compounds with magnetic and non-magnetic R-elements according to the mean-field expression [3]…”

Section: K30 Physica Status Solidi (B) 176mentioning

confidence: 99%

4f–3d Coupling in the Dy₂(Ni_1–xCo_x)₁₇ Compounds

Duc

1993

Physica Status Solidi (b)

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IntroductionIn the rare earth-transition metal intermetallics, it is generally accepted that there are three types of interactions, namely, the R-R interactions between the magnetic moments within the R-sublattice, the T-T interactions between the magnetic moments of the T-sublattice, and the R-T intersublattice interactions. The T-T interactions are direct exchange interactions between the 3d spins, whereas the R-R interactions are indirect, presumably proceeding via the 4f-Sd-Sd-4f mechanism. The R-T interactions are also indirect, being a combination of the intraatomic 4f-5d and interatomic 5d-3d exchange interactions [l]. As a general rule, the latter interactions are found to be antiferromagnetic for electrons residing in a less than half-filled d band (the 5d band) interacting with electrons in a more than half-filled d band (the 3d band). By means of this scheme, it can be understood that the magnetic ordering in the R-T intermetalliccompounds is either of the ferromagnetic type, if R is a light rare earth element, or of the ferrimagnetic type, if R is a heavy rare earth. This was first suggested, on the basis of experiment, by Campbell [l]. Recently, Brooks et al. 121 were able to add to this picture the importance of the 3d-5d hybridization. Following this model, when a moment develope at the T-sites, the energy of spin-up 3d states is lowered, reducing the 3d-5d hybridization for the spin-up states. This lowers the occupation of the 5d spin-up states. The opposite effect occurs for the spin-down states and the 5d moment which is related to the 5d occupation is induced. The 4f-5d and thus the 4f-3d interactions are created. In the R-T compounds having a large magnetic moment of the T-sublattice, i.e. possessing a large 3d band splitting, the hybrized states will have more spin-down character. This leads to an increase of the 4f-3d interactions with increasing T magnetic moment. Experimentally, a decrease of the 4f-3d exchange interactions, i.e. a decrease of the 3d-5d hybridization, with increasing magnetic moment of the T-sublattice (M.l.), has been found for almost all of the R-Fe and R-Co compounds [3 to 61. However, it was shown in [7] that in the compounds, where the 3d magnetism is well established, the variation of M , does not depend strongly on the 3d band splitting, but is mainly governed by the decrease of the 5d magnetic moment. The Brooks model, thus, may directly be examined on a few series of compounds such as R2Nil,, RCo,,Be, RCo,, and RCo,B [7]. In these compounds, the small value of MT is related to a weak 3d band splitting, and any increase in M , is thought to result from the increase of the 3d band splitting. As regards the value of M,, the studies on the nickel-rich R-(Ni, Co) or R-(Ni, Fe) systems can extend the latter group of compounds. The aim of the present note is to evaluate the 4f-3d coupling parameter in the DY,(Nil -xCox)17 compounds by analysing the Curie temperature and the compensation points. The results are discussed on the basis of the Brooks model. -~ ') 90 Nguyen T...

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An evaluation of the R—T spin coupling parameter in the rare earth–transition metal intermetallics

Cited by 35 publications

References 17 publications

Effect of Ni Substitution on the Structural, Magnetic, and Electronic Structure Properties of Gd0.4Tb0.6(Co1−xNix)2 Compounds

Effect of Ni Substitution on the Structural, Magnetic, and Electronic Structure Properties of Gd0.4Tb0.6(Co1−xNix)2 Compounds

Magnetic Properties and the Electronic Structure of the Gd0.4Tb0.6Co2 Compound

4f–3d Coupling in the Dy₂(Ni_1–xCo_x)₁₇ Compounds

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An evaluation of the R—T spin coupling parameter in the rare earth–transition metal intermetallics

Cited by 35 publications

References 17 publications

Effect of Ni Substitution on the Structural, Magnetic, and Electronic Structure Properties of Gd0.4Tb0.6(Co1−xNix)2 Compounds

Effect of Ni Substitution on the Structural, Magnetic, and Electronic Structure Properties of Gd0.4Tb0.6(Co1−xNix)2 Compounds

Magnetic Properties and the Electronic Structure of the Gd0.4Tb0.6Co2 Compound

4f–3d Coupling in the Dy2(Ni1–xCox)17 Compounds

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4f–3d Coupling in the Dy₂(Ni_1–xCo_x)₁₇ Compounds