Conveners
Quantum Phenomena: Quantum Phenomena I
- Yixi Su (JCNS-MLZ)
- Robert Georgii
Quantum Phenomena: Quantum Phenomena II
- Yixi Su (JCNS-MLZ)
- Robert Georgii
Quantum Phenomena: Quantum Phenomena III
- Robert Georgii
- Yixi Su (JCNS-MLZ)
The magnetic state of exchanged biased CoO(20nm)/Co($d_F$) bilayers ($d_F$=5-20nm) was studied by means of polarized neutron reflectometry. By introducing a Nb(20nm) spacer layer between the CoO/Co bilayer and the Al$_2$O$_3$ substrate, we designed a resonator structure with significantly enhanced intensity of the spin-flip (SF) scattering at the position of the optical resonances. For the...
Materials realizing the scaling behavior of the XY model in two dimensions (2D) are sparse. Here we report on comprehensive neutron triple-axis measurements conducted at the FRM2, BER2, and ILL to investigate the critical static and dynamical magnetic fluctuations in the layered ruthenates Ca$_{2}$RuO$_{4}$ (CRO214) and Ca$_{3}$Ru$_2$O$_{7}$ (CRO327). Specifically, we probe the...
Neutron diffraction is used to establish room temperature magnetic ordering within a laminar, MAX phase material, for the first time. This finding is the first "building block" within our search for 2D magnetic materials. A coexistence between FM and antiferromagnetic (AFM) ordering is found at 1.5 K, in agreement with previous DFT calculations.
The model perovskite SrTiO$_{3}$ is well-known for its strongly anharmonic phonon properties underlying the intriguing physics of soft phonon modes. A plethora of unusual thermal transport properties derive from the interplay of ferroelectricity, phonon softening, quantum fluctuations and topological properties, including Poiseuille flow of phonons and the elusive coupling of phonons in...
The quantum spin systems Cu2MBO5 (M = Al, Ga) with the ludwigite crystal structure consist of a structurally ordered Cu2+ sublattice in the form of three-leg ladders, interpenetrated by a structurally disordered sublattice with a statistically random site occupation by magnetic Cu2+ and nonmagnetic Ga3+ or Al3+...
Amorphous magnetic materials are of considerable interest, both from a fundamental and applied point of view. The low coercive field in an amorphous magnet is an important property for its application as a core material in electrical transformers. The structural and magnetic properties of amorphous magnetic systems can be quite complex. The presence of structural as well as magnetic disorder...
Nematicity is ubiquitous in electronic phases of high-$T_c$ superconductors, particularly in the Fe-based systems. We used inelastic neutron and x-ray scattering to extract the temperature-dependent nematic correlation length $\xi$ from the anomalous softening of acoustic phonon modes in Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ and FeSe. In all cases, we find that $\xi$ is well described by a power law...
Transition metal oxides display versatile magnetic phenomena that are mediated by various exchange mechanisms thanks to the localized d-electrons Perovskite manganese oxides (manganates) are archetypal examples of such magnetic transition metal oxides. In manganates, the super-exchange and double-exchange interactions play a major role in determining the magnetic phase. The relative strength...
Novel electronic phases such as nematic electronic textures or unconventional superconductivity (SC) are frequently observed near zero-temperature magnetic instabilities that arise as a function of a non-thermal control parameter such as pressure. Although it is widely believed that the abundant magnetic fluctuations associated with these quantum phase transitions (QPT) are at the origin of...
