Magnetic structure

About: Magnetic structure is a research topic. Over the lifetime, 10787 publications have been published within this topic receiving 207143 citations.

Bandwidth-controlled magnetic and electronic transitions in La 0.5 Ca 0.5 − x Sr x MnO 3 ( 0 x 0 . 5 ) distorted perovskite

Abstract: We have investigated the effect of the increase of the one-electron e g bandwidth (W) on the ferromagnetic and antiferromagnetic transitions in charge ordered La 0.5 Ca 0.5 MnO 3 by substituting bigger Sr 2+ ions for Ca 2+ ions through electrical resistivity and low-field ac-susceptibility measurements as a function of temperature. The system La 0.5 Ca 0.5-x Sr x MnO 3 is shown to undergo structural transitions with increasing x. For x=0.0 and 0.1, the structure is orthorhombic with space group Pnma. For x=0.2, 0.3, and 0.4, the structure is consistent with a monoclinic space group I2/a. The end member (x=0.5) has a tetragonal structure (I4/mcm). T C increases with x monotonically, consistent with the fact that the increase of W enhances double-exchange ferromagnetic interaction. On the other hand, in contrast to the expected monotonic suppression, T N increases initially with Sr concentration, followed by a decrease, finally disappearing for x=0.4. The nonmonotonous variation of T N may indicate a possible change in the type of magnetic structure in the antiferromagnetic state.

Electronic Structure, Magnetic Order and Interlayer Magnetic Couplings in Metallic Superlattices

Abstract: The general trends for the electronic structure of perfect model superlattices AmBn are calculated using a real-space tight·binding model. The magnetic moments distribution and the interlayer magnetic couplings between ferromagnetic layers Am (A=Fe or Co) coupled by non-magnetic (B=V or Ru), nearly ferromagnetic (B=Pd) or antiferromagnetic (B=Cr) spacer layers Bn are obtained as a function of the spacer thickness n. In a first part, we present the model we used for the calculation and the crystallographic structure of the considered superlattices (Fe/V, Fe/Cr, Co/Ru and Co/Pd). These considera­ tions will be applied to the non·magnetic and nearly ferromagnetic cases to derive general trends for the magnetic interlayers couplings. In a second part, we apply the method we presented previously to the superlattices with an antiferromagnetic spacer (Fe,Cr.). Using first a "d" band calculation we show that the interlayer coupling energy can be understood in terms of a strong interfacial antifer­ romagnetic coupling and of a constrained magnetic wall in the Cr layer giving a rapidly oscillating coupling energy. An extension of the previous calculation taking into account the "spd" hybridization does not affect the previous conclusion. Finally we examine the distribu­ tion of magnetic moments and the stability of tilted antiferromagnetic Cr layers and we find that this magnetic structure is nearly degenerate with the collinear antiferromagnetic arrangement.

Toward 2D Magnets in the (MnBi 2 Te 4 )(Bi 2 Te 3 ) n Bulk Crystal.

Abstract: 2D magnets and their engineered magnetic heterostructures are intriguing materials for both fundamental physics and application prospects. On the basis of the recently discovered intrinsic magnetic topological insulators (MnBi2 Te4 )(Bi2 Te3 )n , here, a new type of magnet, in which the magnetic layers are separated by a large number of non-magnetic layers and become magnetically independent, is proposed. This magnet is named as a single-layer magnet, regarding the vanishing interlayer exchange coupling. Theoretical calculations and magnetization measurements indicate that, the decoupling of the magnetic layers starts to emerge from n = 2 and 3, as revealed by a unique slow-relaxation behavior below a ferromagnetic-type transition at Tc = 12-14 K. Magnetization data analysis shows that the proposed new magnetic states have a strong uniaxial anisotropy along the c-axis, forming an Ising-type magnetic structure, where Tc is the ordering temperature for each magnetic layer. The characteristic slow relaxation, which exists only along the c-axis but is absent along the ab plane, can be ascribed to interlayer coherent spin rotation and/or intralayer domain wall movement. The present results will stimulate further theoretical and experimental investigations for the prototypical magnetic structures, and their combination with the topological surface states may lead to exotic physical properties.

Mn moment instability in the TbMn2 intermetallic compound

Abstract: Neutron diffraction experiments have been performed on a TbMn2 single crystal and on Tb(Mn0.96Fe0.04)2 powder samples. The magnetic structure of TbMn2 is metastable poised between two structures, S1 with propagation vector (2/3 2/3 0) and S2 with propagation vector (1/2 1/2 1/2). A transition from S1 to S2 can be induced either by an applied field of 4.5 T at 25 K or by chemical pressure induced by substitution of Mn by Fe. The S2 structure has been studied in Tb(Mn0.96Fe0.04)2. The transition to this structure is accompanied by a huge rhombohedral distortion and the structure itself is notable for the coexistence of magnetic and non-magnetic manganese atoms. This peculiar feature is attributed to instability of the Mn moment combined with frustration of the Mn itinerant antiferromagnetism.