Lattice parameter analysis and studies of thermal expansion show that the orthorhombic CeNi compound is, like CeSn 3 , an intermediate valence compound in which the cerium valence state varies from 3.5 to 3.3 between 4 and 300 K. This compound behaves as an enhanced Pauli paramagnet in which the magnetic susceptibility along the c axis passes through a maximum at around 140 K. Magnetic susceptibility, resistivity and heat capacity measurements are characteristic of an almost magnetic Fermi liquid in which spin fluctuations are present. Unlike the other cerium intermediate valence compounds which are generally cubic, large anisotropic effects due to the local surroundings are observed in CeNi because of its orthorhombic symmetry. All these properties can be understood in the light of the band structure of this type of alloy in which a large hybridization occurs between the Ni 3d electrons and the Ce 5d electrons.

Intermediate valence state of cerium in CeNi

The authors have undertaken a detailed theoretical investigation of the meta-magnetic transition in UCoAl. Using the fixed spin moment method in their calculations they can account for the observed meta-magnetic transition and find that the magnetic properties of UCoAl are dominated by a moment located on the uranium atom. This uranium moment is found to consist of an orbital moment that is larger and anti-parallel to the spin moment. The spin and orbital moments were calculated using the local spin-density approximation and the recently reported formalism for orbital polarisation together with the spin-orbit interaction.

https://iopscience.iop.org/article/10.1088/0953-8984/1/25/012/pdf

Meta-magnetism in UCoAl

The electronic structure of the perovskite La1−xSrxCoO3 has been obtained as a function of Sr substitution and volume from a series of generalized-gradient-corrected, full-potential, spin-density-functional band-structure calculations. The energetics of different spin configurations are estimated using the fixed-spin-moment (FSM) method. From the total energy versus spin magnetic moment curve for LaCoO3 the ground state is found to be nonmagnetic with the Co ions in a low-spin (LS) state, a result that is consistent with the experimental observations. Somewhat higher in energy, we find an intermediate-spin (IS) state with spin moment ∼1.2μB/%f.u. From the anomalous temperature dependent susceptibility along with the observation of an IS state we predict metamagnetism in LaCoO3 originating from an LS-to-IS transition. The IS state is found to be metallic and the high-spin (HS) state of LaCoO3 is predicted to be a half-metallic ferromagnet. With increasing temperature, which is simulated by a corresponding ...

Itinerant metamagnetism and possible spin transition in LaCoO3 by temperature/hole doping

The electronic structure of the perovskite La$_{1-x}$Sr$_x$CoO$_3$ has been obtained as a function of Sr substitution and volume from a series of generalized-gradient-corrected, full-potential, spin-density-functional band structure calculations. The energetics of different spin configurations are estimated using the fixed-spin-moment (FSM) method. From the total energy vs spin magnetic moment curve for LaCoO$_3$ the ground state is found to be nonmagnetic with the Co ions in a low-spin (LS) state, a result that is consistent with the experimental observations. Somewhat higher in energy, we find an intermediate-spin (IS) state with spin moment $\sim$1.2 $\mu_{B}$/f.u. 
From the anomalous temperature dependent susceptibility along with the observation of an IS state we predict metamagnetism in LaCoO$_3$ originating from an LS-to-IS transition. The IS state is found to be metallic and the high-spin (HS) state of LaCoO$_3$ is predicted to be a half-metallic ferromagnet. With increasing temperature, which is simulated by a corresponding change of the lattice parameters we have observed the disappearence of the metamagnetic solution that is associated with the IS state. The FSM calculations on La$_{1-x}$Sr$_x$CoO$_3$ suggest that the hole doping stabilizes the IS state and the calculated magnetic moments are in good agreement with the corresponding experimental values. Our calculations show that the HS state cannot be stabilized by temperature or hole doping since the HS state is significantly higher in energy than the LS or IS state. Hence the spin-state transition in LaCoO$_3$ by temperature/hole doping is from an LS to an IS spin state and the present work rules out the other possibilities reported in the literature.

https://arxiv.org/pdf/cond-mat/0104308.pdf

Itinerant metamagnetism and possible spin transition in LaCoO$_3$ by temperature/hole doping

The multipole moment is an established concept of electrons in solids. Entanglement of spin, orbital, and sublattice degrees of freedom is described by the multipole moment, and spontaneous multipole order is a ubiquitous phenomenon in strongly correlated electron systems. In this paper, we present group-theoretical classification theory of multipole order in solids. Intriguing duality between the real-space and momentum-space properties is revealed for odd-parity multipole order which spontaneously breaks inversion symmetry. Electromagnetic responses in odd-parity multipole states are clarified on the basis of the classification theory. A direct relation between the multipole moment and the magnetoelectric effect, Edelstein effect, magnetopiezoelectric effect, and dichromatic electron transport is demonstrated. More than 110 odd-parity magnetic multipole materials are identified by the group-theoretical analysis. Combining the list of materials with the classification tables of multipole order, we predict emergent responses of the candidate materials.

Group-theoretical classification of multipole order: Emergent responses and candidate materials

Compounds of rare earth and transition metals exhibit unusual and quite different behaviour. In order to explain the large variety of magnetic behaviour, we show that one needs the electronic structure in these compounds. We report on the existing calculations and give the general shape of the density of states in these intermetallic compounds. We discuss particularly the case of the TM2 compounds (T = rare earth ; M = Fe, CO, Ni). The most unusual behaviour appears with the cobalt compounds where the cobalt within the rare earth serles can be magnetic or not. We review the theories on the TCo2 series and explain the magnetic behaviour by the position of the Fermi level in this compound in a steep decrease of the density of states. This leads to a klnd of collective metamagnetism. This is confirmed by experiments that we review. Unusual behaviour of other compounds wlth cobalt can be understood following the same lines as TCo2 and is discussed.

/pdf/magnetism-of-the-rare-earth-3d-theoretical-review-2wtf51s246.pdf

Magnetism of the rare earth, 3d { Theoretical review

The magnetic structures of Ce3Al11: a single crystal study

Evidence for 5d anisotropic negative polarization along the Ce chains in CeRh3B2

Anomalous magnetic behavior of cerium in Ce2Sn5 and Ce3Sn7, two superstructures of CeSn3

From magnetic susceptibility and magnetic form factor measurements on stoichiometric and non-stoichiometric CeSn 3 single crystals, it has been shown that the 5d contribution to Ce magnetism which appears at low temperatures exists only in the stoichiometric sample and is destroyed by the presence of defects.

F. Givord

Papers

Magnetism of the rare earth, 3d { Theoretical review

The magnetic structures of Ce3Al11: a single crystal study

Evidence for 5d anisotropic negative polarization along the Ce chains in CeRh3B2

Anomalous magnetic behavior of cerium in Ce2Sn5 and Ce3Sn7, two superstructures of CeSn3

Coherence effects and 5d contribution to the magnetism of Ce in CeSn3