Correlated-electron theory of strongly anisotropic metamagnets

Held, Karsten; Ulmke, M.; Blümer, N.; Vollhardt, D.

doi:10.1103/physrevb.56.14469

Cited by 39 publications

(28 citation statements)

References 52 publications

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“…The small ordered moment may result from the combination of quantum fluctuations within the spin channel, spin-orbit coupling and the small Hubbard gap. The latter gives rise to enhanced fluctuations both in the charge and in the orbital channel and thus may contribute significantly to the reduction of the ordered moment [118] 13 . Nevertheless, the uncertainty of the theoretical predictions for the crystal-field splitting is too large to rule out a finite contribution from orbital fluctuations.…”

Section: Orbital Excitations In Rtio 3 (R = La Sm and Y)mentioning

confidence: 99%

Optical study of orbital excitations in transition-metal oxides

et al. 2005

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Collective orbital excitations in orbitally ordered YVO3 and HoVO3 E Benckiser, R Rückamp, T Möller et al. Abstract. The orbital excitations of a series of transition-metal compounds are studied by means of optical spectroscopy. Our aim was to identify signatures of collective orbital excitations by comparison with experimental and theoretical results for predominantly local crystal-field excitations. To this end, we have studied TiOCl, RTiO 3 (R = La, Sm and Y), LaMnO 3 , Y 2 BaNiO 5 , CaCu 2 O 3 and K 4 Cu 4 OCl 10 , ranging from early to late transition-metal ions, from t 2g to e g systems, and including systems in which the exchange coupling is predominantly three-dimensional, one-dimensional or zero-dimensional. With the exception of LaMnO 3 , we find orbital excitations in all compounds. We discuss the competition between orbital fluctuations (for dominant exchange coupling) and crystal-field splitting (for dominant coupling to the lattice). Comparison of our experimental results with configuration-interaction cluster calculations in general yields good agreement, demonstrating that the coupling to the lattice is important for a 7 Author to whom any correspondence should be addressed. quantitative description of the orbital excitations in these compounds. However, detailed theoretical predictions for the contribution of collective orbital modes to the optical conductivity (e.g. the line shape or the polarization dependence) are required to decide on a possible contribution of orbital fluctuations at low energies, in particular, in case of the orbital excitations at ≈0.25 eV in RTiO 3 . Further calculations are called for which take into account the exchange interactions between the orbitals and the coupling to the lattice on an equal footing. Contents

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Section: Orbital Excitations In Rtio 3 (R = La Sm and Y)mentioning

confidence: 99%

Optical study of orbital excitations in transition-metal oxides

et al. 2005

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“…1 A rich variety of interesting magnetic phenomena, i.e., magnetic field induced antiferromagnetic ͑AFM͒ to ferromagnetic ͑FM͒ transformations, so-called metamagnetic transitions, have also been observed in bulk materials with naturally layered crystal structures where layers containing magnetic ions also are separated by nonmagnetic layers. 2,3 Experimental data on metamagnetic transitions have been reported for various 3d-͓e.g., FeX 2 , CoX 2 , XϭCl, Br ͑Ref. 4͔͒, 4 f -͓e.g., R 7 Rh 3 , RϭTb, Dy, Ho ͑Ref.…”

Section: Introductionmentioning

confidence: 99%

Reversible spin-flop and irreversible metamagneticlike transitions induced by a magnetic field in the layeredGd5Ge4antiferromagnet

et al. 2004

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Temperature and magnetic field dependencies of the magnetization of single crystal Gd 5 Ge 4 indicate antiferromagnetic coupling along the c direction below 130 K. Both a reversible spin-flop transition when a magnetic field of ∼8.4kOe is applied along the cdirection, and irreversible metamagneticlike transitions when a 20 kOe or greater magnetic field is applied at 4.3 K along any of the three crystallographic axes are observed. Although Gd3+ ions have negligible single ion anisotropy, the metamagnetic transitions and magnetization of Gd 5 Ge 4 in the ferromagnetic state depend on the crystallographic direction reflecting the anisotropy of the exchange interactions due to the distinctly layered Sm 5 Ge 4 -type crystal structure. Keywords Physics and Astronomy, Materials Science and Engineering Disciplines Condensed Matter Physics | Metallurgy CommentsThis article is from Physical Review B 69 (2004) Temperature and magnetic field dependencies of the magnetization of single crystal Gd 5 Ge 4 indicate antiferromagnetic coupling along the c direction below 130 K. Both a reversible spin-flop transition when a magnetic field of ϳ8.4 kOe is applied along the c direction, and irreversible metamagneticlike transitions when a 20 kOe or greater magnetic field is applied at 4.3 K along any of the three crystallographic axes are observed. Although Gd 3ϩ ions have negligible single ion anisotropy, the metamagnetic transitions and magnetization of Gd 5 Ge 4 in the ferromagnetic state depend on the crystallographic direction reflecting the anisotropy of the exchange interactions due to the distinctly layered Sm 5 Ge 4 -type crystal structure.

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“…Metamagnetism, was originally proposed by Wohlfarth 26 27 , 28 and by Bedell 29 and others in the context of Fermi liquid theory and the magnetic field dependence of Landau's Fermi liquid parameters. More recent work in a microscopic description of metamagnetism in heavy fermions can be seen in Kusminsky et.…”

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Universality in the magnetic response of metamagnetic metals

et al. 2014

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We report in this paper, measurements of the nonlinear susceptibility χ 3 (T) in the metamagnetic heavy fermion (HF) compound UPt 3 . At high temperatures, χ 3 (T) < 0 and small. It turns positive for T ≤ 35K, forms a peak at T  10K and then decreases to zero with further decreasing temperature. The peak in χ 3 occurs at a temperature T 3 roughly half of T 1 , the temperature of the maximum in the linear susceptibility. We present results on URu 2 Si 2 and UPd 2 Al 3 to show that this feature is common to other HF materials. A two level model to describe the metamagnetic transition, with separation between the levels being the only energy scale, captures all experimentally observed features. *bss2d@virginia.edu -to whom all correspondence should be addressed.2 Given the myriad ways in which one can arrange atoms to form crystal structures and the possibilities of placing electrons in them the discovery of a common behavioral pattern in the electronic properties often leads to new microscopic insights. In metals, recent discoveries of universal rules such as the Kadowaki-Woods relation 1 which connects the electron effective mass enhancement to the temperature dependence of the resistivity in Fermi liquid systems, the constancy of the Wilson ratio 2 , the Homes plot 3 and other similar scaling laws have assisted in identifying the dominant energy scales, and helped in insights to build microscopic theories.Our purpose in this paper is to show that the magnetic response of many electronic materials that undergo a metamagnetic transition also exhibit universal features in their nonlinear susceptibility. Along with a jump in the magnetization at a critical field, H m , metamagnetism also entails a positive nonlinear susceptibility at low temperatures (it is negative at high temperatures), a peak in the linear susceptibility  1 (T) at a temperature T 1 , a peak in the leading order nonlinear susceptibility  3 (T) >0 at a lower temperature T 3 . These are features widely seen in different materials with diverse lattice structures and electronic properties. Hirose et. al 4 have noted the correlation between H m and the temperature T 1 of the maximum in  1 (T). Goto et. al pointed out earlier that the metamagnetic field H m also correlates with the value of  1 (T) at its maximum 5 . Both of these correlations, found in a number of materials, indicate a dominant presence of one energy scale. In the following we report a new correlation, one between the peak temperatures T 3 for  3 (T) and T 1 namely T 3 =T 1 /2. We also present a new model that captures all of these correlations.For purposes of illustrating this universality we consider the heavy electron class of materials. Within these systems metamagnetic behavior is seen in several uranium compounds 6,7,8,9,10 , cerium compounds 11,12,13,14 , as well as in the ytterbium compounds 15 . Most of these systems possess either hexagonal or tetragonal symmetry. The same behavior is also observed in the skutterudite structure in PrOs 4 Sb 12 a moderately heavy...

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Correlated-electron theory of strongly anisotropic metamagnets

Cited by 39 publications

References 52 publications

Optical study of orbital excitations in transition-metal oxides

Optical study of orbital excitations in transition-metal oxides

Reversible spin-flop and irreversible metamagneticlike transitions induced by a magnetic field in the layeredGd5Ge4antiferromagnet

Universality in the magnetic response of metamagnetic metals

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