scholarly journals Molecular Spin Dynamics Analysis of Complex Magnetic Structure on the FCC Lattice in Itinerant Electron System

2015 ◽  
Vol 75 ◽  
pp. 625-633
Author(s):  
Yoshiro Kakehashi ◽  
Shota Nohara ◽  
Sumal Chandra ◽  
Takashi Uchida
Keyword(s):  
Magnetic Structure ◽  
Spin Dynamics ◽  
Electron System ◽  
Itinerant Electron ◽  
Dynamics Analysis ◽  
Fcc Lattice ◽  
Molecular Spin

Neutron Studies of the Iron-based Family of High Tc Magnetic Superconductors

2008 ◽  
Vol 1148 ◽  
Author(s):  
Jeffrey W. Lynn
Keyword(s):  
Magnetic Order ◽  
Spin Dynamics ◽  
Magnetic Scattering ◽  
Anisotropic Pressure ◽  
Itinerant Electron ◽  
Superconducting Transition ◽  
Orthogonal Direction ◽  
Magnetic Structures ◽  
Se Doping ◽  
Iron Based

AbstractWe briefly review recent neutron scattering investigations carried out at the NIST Center for Neutron Research on the crystal structures, magnetic structures, and spin dynamics of the iron-based ROFe(As,P) (R=La, Ce, Pr, Nd), and (Ba,Sr,Ca)Fe2As2 systems. All the undoped materials exhibit universal behavior, where a tetragonal-to-orthorhombic structural transition occurs between ˜100−220 K, below which the systems become antiferromagnets. The magnetic structure within the a-b plane consists of chains of parallel Fe spins that are coupled antiferromagnetically in the orthogonal direction, with an ordered moment typically less than one Bohr magneton. Hence these are itinerant electron magnets, with a spin structure that is consistent with Fermi-surface nesting and a spin wave bandwidth ˜200 meV. The rare-earth moments order antiferromagnetically at low T like ‘conventional’ magnetic-superconductors. With doping, the structural and magnetic transitions are suppressed in favor of superconductivity, with superconducting transition temperatures up to 56 K, while the Ce crystal field linewidths are affected when superconductivity sets in. The application of pressure in CaFe2As2 transforms the system from a magnetically ordered orthorhombic material to a ‘collapsed’ non-magnetic tetragonal system which is superconducting at lower T when anisotropic pressure is applied. Fe1+xTe shows a transition from a monoclinic to orthorhombic low T structure with increasing x, and a crossover from commensurate to incommensurate magnetic order. Se doping suppresses the magnetic order, while incommensurate magnetic scattering is observed in the superconducting regime.

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