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- Creator:
- Cooper, Bernard R., Kioussis, Nicholas G., Sheng, Q.G., and Wills, John M.
- Description:
- For partially delocalized correlated f-electron systems, the key aspect of the electronic behavior is the hybridization of f electrons with the non-f-band electrons. This gives unusual properties including suppressed crystal-field splitting and highly anisotropic ordered magnetism. To improve the general understanding and to make the theory materially predictive, a technique is being developed to evaluate absolutely the parameters of the correlated electron model Hamiltonian, and then to use these to predict observed phenomenology including details of magnetic ordering such as magnetic structures and transitions between structures. The most difficult quantity to predict is the magnetic ordering temperature, among other reasons because it depends on the hybridization strength in a highly nonlinear way. Previously Wills and Cooper have reported on a technique involving a nonconventional electronic structure calculation based on treating the/electron as a resonant state in a solid-state environment to evaluate the hybridization. As an independent check on the evaluation of hybridization, here a conventional tight binding parametrization scheme was used to evaluate the hybridization. These results are compared both with previous results and with experiment for the magnetic ordering temperature and crystal-field dressing of Ce compounds, and the situation introduced by the relative degrees of nonlinearity for the crystal-field and magnetic ordering response to the hybridization strength are commented on.
- Resource Type:
- Article
- Identifier:
- 0021-8979
- Campus Tesim:
- Northridge
- Creator:
- Sheng, Q.G., Cooper, Bernard R., Wills, John M., and Kioussis, Nicholas G.
- Description:
- Over the past decade, we have : (1) developed phenomenological theory for the behavior of "well-ordered" magnetic states of moderately delocalized light rare earth and actinide systems (characteristically obtaining unusual anisotropic magnetism in agreement with experiment) ; (2) developed theory and computational technique to synthesize first principles electronic structure information into that phenomenological theory to make it materially predictive. As discussed below, the resulting theory allows us to predict the triggering of an instability from unusual anisotropic, but well-ordered, magnetism to an unstable state. The unstable state can be either of a valence fluctuation type or of what probably is a heavy fermion type, and the detailed way in which these two types of instability is triggered differs.
- Resource Type:
- Article
- Identifier:
- 1155-4304
- Campus Tesim:
- Northridge
- Creator:
- Sheng, Q.G., Cooper, Bernard R., Wills, John M., and Kioussis, Nicholas G.
- Description:
- Over the past decade, we have: (1) developed phenomenological theory for the behavior of "well-ordered" magnetic states of moderately delocalized light rare earth and actinide systems (characteristically obtaining unusual anisotropic magnetism in agreement with experiment); (2) developed theory and computational technique to synthesize first principles electronic structure information into that phenomenological theory to make it materially predictive. As discussed below, the resulting theory allows us to predict the triggering of an instability from unusual anisotropic, but well-ordered, magnetism to an unstable state. The unstable state can be either of a valence fluctuation type or of what probably is a heavy ferrnion type, and the detailed way in which these two types of instability is triggered differs.
- Resource Type:
- Article
- Identifier:
- 0021-8979
- Campus Tesim:
- Northridge
- Creator:
- Sheng, Q.G., Cooper, Bernard R., Thevenot, J., and Kioussis, Nicholas G.
- Description:
- There is a great change in the nature of the magnetic ordering on going from CeIn3, a local moment antiferromagnetic system, to CePb3, a heavy fermion itinerant antiferromagnetic system, both of which have Cu3Au crystal structure. We have applied ab initio electronic structure calculations, based on the linear-muffin-tin-orbital method, and a phenomenological theory of orbitally driven magnetic ordering, to study the effects of the band-f hybridization-induced interactions and the band-f exchange-induced interactions, pertinent to the magnetic behavior of these systems. The position of the Ce 4 f energy level relative to the Fermi energy and the intra-atomic Coulomb interaction are obtained from a sequence of three total-energy supercell calculations with two, one and zero f electrons in the Ce 4 f core. The calculations elucidate the origins in the electronic structure of the variation of the f-state resonance width characterizing the strength of the hybridization and the density of states at the Fermi energy characterizing the number and character of band states available for hybridization. We present results for the hybridization potential and the hybridization-induced exchange interactions on going from CeIn3 to CePb3, where the only obvious change is the addition of an anion p electron.
- Resource Type:
- Article
- Identifier:
- 0021-8979
- Campus Tesim:
- Northridge
- Creator:
- Sheng, Q.G., Cooper, Bernard R., Yu, H.J., Wills, John M., and Kioussis, Nicholas G.
- Description:
- The isostructural uranium monopnictides and monochalcogenides have become prototype systems in actinide research with respect to their unusual magnetic properties. We have investigated the origins in the electronic structure of the variation in magnetic behavior as the degree of 5f-electron localization changes from localized to itinerant on going up the pnictogen or chalcogen column, thus decreasing the U-U separation. We have applied a synthesis of: (1) A phenomenological theory of orbitally driven magnetic ordering which includes both the hybridization-induced and the RKKY exchange interactions on an equal footing, and (2) Ab initio electronic structure calculations, based on the linear-muffin-tin-orbital method, allowing a first-principles evaluation of the parameters entering the model Hamiltonian. We have investigated systematically characteristic trends and changes of the 5f-state resonance width, the hybridization potential, and the hybridization-induced and RKKY exchange interactions with chemical environment, on going down the pnictogen or chalcogen column and on going from the weakly hybridizing pnictides to the more strongly hybridizing chalcogenides.
- Resource Type:
- Article
- Identifier:
- 0021-8979
- Campus Tesim:
- Northridge