Electronically Induced Ferromagnetic Transitions inSm5Ge4-Type Magnetoresponsive Phases

Abstract

The correlation between magnetic and structural transitions in Gd(5)Si(x)Ge(4-x) hampers the studies of valence electron concentration (VEC) effects on magnetism. Such studies require decoupling of the VEC-driven changes in the magnetic behavior and crystal structure. The designed compounds, Gd(5)GaSb(3) and Gd(5)GaBi(3), adopt the same Sm(5)Ge(4)-type structure as Gd(5)Ge(4) while the VEC increases from 31 e(-)/formula in Gd(5)Ge(4) to 33 e(-)/formula in Gd(5)GaPn(3) (Pn: pnictide atoms). As a result, the antiferromagnetic ground state in Gd(5)Ge(4) is tuned into the ferromagnetic one in Gd(5)GaPn(3). First-principles calculations reveal that the nature of interslab magnetic interactions is changed by introducing extra p electrons into the conduction band, forming a ferromagnetic bridge between the adjacent (∝)(2)[Gd(5)T(4)] slabs.

Competition between Direct and Indirect Exchange Couplings in MnFeAs: A First-Principles Investigation

“…In general, there are two types of indirect magnetic couplings, namely, RKKY and superexchange interactions. 38−42 The nature of RKKY interactions is determined by the density of conduction electrons and metal−metal distances; 38,39 so, if the indirect coupling is very sensitive to distance, it could be a RKKY-type interaction. In contrast, the nature of superexchange interactions between metal atoms is controlled by their orbital overlap with a shared (bridging) ligand.…”

Anomalous effects of Sc substitution and processing on magnetism and structure of (Gd1−xScx)5Ge4

“…13 All of these effects are rooted in strong magnetoelastic coupling, and the resulting MSTs can be controlled by external thermodynamic parameters such as temperature, hydrostatic pressure or uniaxial stress, and applied magnetic field, in addition to tuning electronic structures via chemical substitution. 14,15,16 Gd5Ge4, one of most studied compounds in the R5T4 family, exhibits an isothermal magnetic field-induced MST between the Sm5Ge4-type orthorhombic (O-II) and the Gd5Si4-type orthorhombic (O-I) structures below 30 K. The transition is irreversible at ~9 K and below, partially reversible between 9 and ~21 K, and fully reversible above 21 K. 17,18 Further, the equivalent transition can be temperature-induced in constant applied dc magnetic fields starting at 10-14 kOe (depending on the sample), and it remains incomplete and partially irreversible 19,20 in magnetic fields lower than 30 kOe. Formation of glass-like kinetically-arrest state(s) is responsible for the irreversibility of the AFM O-II ↔ FM O-I transition in Gd5Ge4 and, in addition to temperature and magnetic field, these frozen states can be controlled by hydrostatic pressure.…”

Many body population trapping in ultracold dipolar gases

“…Polar molecules are particularly interesting in this context, as they can interact via long-range dipolar forces, which can induce yet another kind of frustration. In particular, dipolar lattice gases have been proposed to simulate various quantum phases and exotic phenomena, such as supersolidity [3,4], quantum magnetism [5], topological states [6,7], exotic pair-superfluidity [8], etc. Experimental progress towards creation of quantum degenerate gas of ground state polar molecules has been spectacular over the last years [9][10][11][12], leading, for instance, to realization of quantum spin models using fermionic molecules [13] or dipolar Chromium atoms [14].…”

“…Theoretically it is a challenge to investigate the properties of these strongly interacting molecules trapped in an optical lattice [15]. The standard approach based on Bose-Hubbard models limited to the lowest Bloch band [3][4][5][6][7][8] becomes inapplicable due to strong interaction induced coupling between the bands. In this paper we provide a novel route to describe such strongly interacting systems.…”