Electrical resistivity, Curie temperature and band structure in Tb0.27Dy0.73(Fe1−xCox)2 intermetallics

doi:10.1016/j.intermet.2013.05.019

Intermetallics

Volume 42, November 2013, Pages 99-106

https://doi.org/10.1016/j.intermet.2013.05.019 Get rights and content

Highlights

•
Electrical resistivity studies of the complete Tb_0.27Dy_0.73(Fe_1−xCo_x)₂ series.
•
ρ₀, ρ_f(T) and ρ_m(T) contributions are separated. θ_D and T_C are determined.
•
The 3d and 4s bands are characterized by FLAPW electronic structure calculations.
•
Magnetic moments of TM atoms and the 3d or 4s band splitting energies correlate.
•
T_C is described in relation with magnetic moments or 3d band splitting energies.

Abstract

Electrical resistivity studies performed in a wide temperature range across the complete Fe/Co substituted Tb_0.27Dy_0.73(Fe_1−xCo_x)₂ intermetallic series, with a borderline compound Tb_0.27Dy_0.73Fe₂ known as Terfenol-D are presented. Parameters characterizing the dependence of resistivity on temperature, including the Debye temperature, are determined. Residual, phonon and magnetic contributions are separated from electrical resistivity. The magnetic contribution to electrical resistivity is applied to estimate Curie temperatures. Regions of weak and strong ferromagnetism of the transition metal sublattice are evidenced. The Curie temperature increases with x, approaches a maximum for x = 0.3 and reduces across the rest of the series. Some results of electronic band structure calculations using the Full-Potential Linearized Augmented Plane Waves (FLAPW) method are also presented. A distribution function for the densities of 3d states is introduced and a formula to estimate the band splitting energy is proposed. The obtained 3d and 4s band splitting energies for iron, cobalt and average for transition metal are presented. The Curie temperature across the Tb_0.27Dy_0.73(Fe_1−xCo_x)₂ system is described using a formula relating to both the FLAPW calculated magnetic moments and the statistical properties of the substituted transition metal sublattice.

Introduction

The heavy rare earth (R)–transition metal (M) ferrimagnetic intermetallics of Laves phases, RM₂-type, are investigated extensively out of fundamental scientific interest and for their versatile practical applications [1], [2], [3], [4], [5], [6], [7].

The ferrimagnetism of heavy rare earth (R)–transition metal (M) compounds results from the coexistence of rare earth 4f(5d) and transition metal 3d electron magnetism. The significance of 4f electrons and especially of 5d electrons has previously been studied elsewhere [6], [7], [8]. Although the magnetic properties of these intermetallics depend on both the 4f(5d) electrons of the rare earth sublattice and the 3d band-type electrons of the transition metal sublattice, the role of 3d electrons seems to be predominant [8], [9], [10].

For practical reasons, RFe₂ type materials have previously been studied because of their strong magnetostriction, with especially large magnetostriction observed for the TbFe₂ compound [11], [12], [13]. In order to compensate the magnetocrystalline anisotropy while maintaining sufficient magnetostriction, the pseudobinary intermetallic series Tb_1−xDy_xFe₂ was tested. It was found that for the compound Tb_0.27Dy_0.73Fe₂, commercially called Terfenol-D, the room temperature magnetocrystalline anisotropy is minimized, and the magnetostriction, although reduced compared to the value for TbFe₂, is sufficiently maintained [11], [12], [13].

Recently both Terfenol-D and other intermetallics of the series Tb_xDy_1−xFe₂ have been intensively tested as strongly magnetostrictive constituents for composites or laminates with piezoceramics or polymers in order to obtain new materials with a giant magnetoelectric effect [14], [15], [16], [17].

On the other hand, the substitution of iron by another transition metal in an RFe₂ type system can be applied as a driving force to change the number n of 3d electrons (calculated per transition metal atom) in the transition metal M-sublattice and thus to change 3d-band properties and the electrical, magnetic or hyperfine interaction properties which are related to them [9].

Previously, the results of Fe/Co substitution in the M-sublattice were experimentally studied in the Tb_0.27Dy_0.73(Fe_1−xCo_x)₂ intermetallics using the ⁵⁷Fe Mössbauer effect [18], [19], [20]. It can be marked that in these compounds the rare earth contribution is the same across the series. Some results of electronic band structure calculations using the Full-Potential Linearized Augmented Plane Waves (FLAPW) method have also been reported. In particular, the idea of regions of weak and strong ferromagnetic behaviour of M elements has been discussed [18].

In contrast to the magnetic properties, the electrical properties of the investigated system are less known and the origin of these properties and their relations to magnetism and electronic band structure would seem still to be an open topic for research. Therefore, it was revealing to study the influence of the 3d-band electron population on both the electrical and magnetic properties of this Fe/Co substituted series which starts with Terfenol-D.

Consequently, in this paper the results of electrical resistivity measurements performed in a wide temperature range and further electronic band structure calculations by the FLAPW method for the complete Tb_0.27Dy_0.73(Fe_1−xCo_x)₂ intermetallic system are presented and discussed. The FLAPW results relating to the statistical properties of the M-sublattice are used to describe the Curie temperature dependence on Fe/Co substitution.

Section snippets

Materials and crystal structure

The synthesis, annealing process and X-ray crystal structure studies of polycrystalline materials Tb_0.27Dy_0.73(Fe_1−xCo_x)₂ (x = 0,0.1,…,0.9 and 1.0) have been previously reported elsewhere [18], [19], [20]. It is worth mentioning that a cubic, Fd3m, MgCu₂-type, C15 clean crystal phase was observed for all investigated compounds and the unit cell parameter for complete data of the series, described by the following numerical formula a(x) = (−0.104x² − 0.029x + 7.337) Å, decreases softly

FLAPW studies

The electronic band structures of Tb_0.27Dy_0.73(Fe_1−xCo_x)₂ intermetallics were calculated by an ab-initio self-consistent Full - Potential Linearized Augmented Plane Waves (FLAPW) method as implemented in the WIEN2K code [40]. Some results of performed calculations i.e. individual Fe, Co and average transition metal sublattice densities of states and magnetic moments have been previously described in part elsewhere [18]. Below the main focus is on the properties of the 3d and 4s transition metal

Experimental and FLAPW results

As yet, there is no analytical formula for a number of the properties observed experimentally for metallic ferro- or ferrimagnets with a band structure. As a step towards their explanation, it is useful to take into account correlations between experimental and FLAPW calculated dependencies.

Summary

Electrical, magnetic and band properties have been measured and calculated for the Tb_0.27Dy_0.73(Fe_1−xCo_x)₂ series of intermetallics.

Fe/Co replacement in the Tb_0.27Dy_0.73(Fe_1−xCo_x)₂ series adds an additional 3d electron per transition metal atom. As a result, it reduces the lattice parameter and the unit cell volume [18], [19], [20], thus reducing with x the average distance between the neighbouring transition metal atoms. Consequently, the band structure, especially the 3d band structure of the

Acknowledgements

Supported partially by The Polish Ministry of Science and Higher Education, project no. R015000504 and partially by AGH, project no. 11.11.220.01.

References (43)

E. Burzo et al.
Magnetic properties of RCo₅-based systems
J Alloys Compd
(2011)
B. Gicala et al.
Two Slater-Pauling dependences for Dy-3d metal compounds
Phys Lett A
(1994)
B. Gicala et al.
Magnetic hyperfine fields of Dy_x(Fe−Co)_y compounds
Solid State Commun
(1995)
A.E. Clark
Magnetostrictive rare earth-Fe₂ compounds
W. Bodnar et al.
Hyperfine interactions and electronic band structure in Tb_0.27Dy_0.73(Fe_1−xCo_x)₂ compounds
J Alloys Compd
(2010)
W. Bodnar et al.
Electrical resistivity and Mössbauer effect investigations on Tb_0.27Dy_0.73(Mn_1−xCo_x)₂ intermetallics
J Alloys Compd
(2010)
P. Stoch et al.
Electrical resistivity and Mössbauer effect studies of Dy(Mn_0.4−xAl_xFe_0.6)₂ and Dy(Mn_1−xFe_x)₂ intermetallics
J Alloys Compd
(2005)
P. Stoch et al.
Electrical resistivity studies of Dy(Fe_1−xCo_x)₂ compounds
J Alloys Compd
(2005)
K. Gu et al.
The magnetocaloric effect in (Dy,Tb)Co₂ alloys
J Alloys Compd
(2007)
S. Kishore et al.
Magnetization studies and crystalline electric field effects in Dy_0.73Tb_0.27Co₂
Solid State Commun
(1997)

S. Kishore et al.

Effect of hydrogen on the magnetic properties of Dy_0.73Tb_0.27Fe_2−xCo_x [x = 0.5, 1.0, 2.0]

Physica B

(1996)

J. Pszczoła et al.

Ordering temperatures of the heavy rare earth-iron intermetallics

J Magn Magn Mater

(1986)

K.N.R. Taylor

Intermetallic rare-earth compounds

Adv Phys

(1971)

K.H.J. Buschow

Rare earth compounds

E. Burzo et al.

A.M. Tishin et al.

The magnetocaloric effect and its applications

(2003)

E. Burzo et al.

On the R 5d band polarization in rare-earth-transition metal compounds

J Phys Condens Matter

(2011)

I.A. Campbell

Indirect exchange for rare earths in metals

J Phys F Met Phys

(1972)

J.R. Cullen et al.

Magnetostriction and structural distortion in rare-earth intermetallics

Phys Rev B

(1977)

P. Westwood et al.

Microstructure and magnetostriction in rare-earth-iron alloys

J Appl Phys

(1988)

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Electrical resistivity, Curie temperature and band structure in Tb0.27Dy0.73(Fe1−xCox)2 intermetallics

Highlights

Abstract

Introduction

Section snippets

Materials and crystal structure

FLAPW studies

Experimental and FLAPW results

Summary

Acknowledgements

J Alloys Compd

Phys Lett A

Solid State Commun

J Alloys Compd

J Alloys Compd

J Alloys Compd

J Alloys Compd

J Alloys Compd

Solid State Commun

Physica B

J Magn Magn Mater

Intermetallic rare-earth compounds

Adv Phys

Rare earth compounds

The magnetocaloric effect and its applications

On the R 5d band polarization in rare-earth-transition metal compounds

J Phys Condens Matter

Indirect exchange for rare earths in metals

J Phys F Met Phys

Magnetostriction and structural distortion in rare-earth intermetallics

Phys Rev B

Microstructure and magnetostriction in rare-earth-iron alloys

J Appl Phys

Electrical resistivity, Curie temperature and band structure in Tb_0.27Dy_0.73(Fe_1−xCo_x)₂ intermetallics