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Univ. Paris-Saclay
Strongly correlated quantum materials and magnetism
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This scientific axis encompasses research activities on a large variety of magnetic and/or strongly correlated electron systems. Included are studies of unconventional superconductors (cuprates, pnictides), geometrically frustrated pyrochlore magnets (spin ices), novel magnetic orders in 4f-electron systems (heavy fermions, Kondo insulators), multiferroic compounds with interplay between electric and magnetic orders, manganites with giant magnetoresistance properties, and molecular magnets.

The techniques involved are neutron diffraction and inelastic neutron scattering, with the optional use of polarized neutrons.

 

Current research

 

Presentation of the "Strongly correlated quantum materials and magnetism" axis (Sept. 2011).

 
#1978 - Màj : 14/05/2019
Voir aussi
Geometrical frustration in the pyrochlore lattice: spin liquids and spin ices : In chemically ordered compounds with short-range magnetic interactions, geometrical frustration appears when all interactions cannot be satisfied simultaneously due to the lattice geometry. A well-known example is a triangle of antiferromagnetically coupled spins. This frustration results in a strong degeneracy of the ground state, since many configurations have the same energy.
Molecular magnetism and photomagnetism : Molecular magnetism is a relatively new field of research, which has attracted growing interest among physicists since the discovery, fifteen years ago, of the first “single molecule magnet” (SMM), Mn12-acetate, which behaves as a magnet at the molecular scale below a blocking temperature of 3 K.
Multiferroic materials : Studies conducted over the past few decades came to the conclusion that ferroelectricity and magnetism tend to be mutually exclusive, and interact only weakly with each other when they do coexist. The recent discovery of multiferroic materials, in which ferroelectricity and magnetism are intimately coupled, has completely changed these established views, opened routes to new technological applications, and has forced physicists to reconsider some long-accepted ideas [1].
Novel electronic and magnetic properties in 4f-electron systems :   4f electrons are known to be more localized than d electrons and subject to strong spin-orbit coupling. Instabilities of otherwise magnetic 4f states occur mainly in metallic compounds as a result of hybrid­ization with conduction band states, as described in the well-known Anderson model.
Observation of a magnetic "blue phase" in an itinerant magnet : Blue phases often appear in chiral liquid crystals as arrangements of so-called “double-twist cylinders”, characterized by twisting in all directions perpendicular to the cylinder axis [1]. Magnetic moments in chiral magnets tend to form spirals, and one can thus speculate on the existence of magnetic “blue phases”.
Strong correlation in CMR manganites : Among the many novel phenomena encountered in strongly-correlated electron systems, specific effects originating from the interplay of different degrees of freedom (lattice, electron charge, spin and orbital angular momentum) have aroused particular interest.
Unconventional superconductivity: neutron spectroscopy and theory : In the last two decades, new superconducting (SC) compounds, exhibiting surprisingly high critical temperatures (Tc), have been discovered. In contrast to conventional superconductors, the SC order parameter is not isotropic, neither in cuprates nor in Fe-based systems. This ignited a search for new SC pairing mechanisms based on the existence of rather strong electronic interactions.

 

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