We show evidence that the competition between the antiferromagnetic metallic phase and the charge- and orbital-ordered insulating phase at the reentrant phase boundary of a layered manganite, LaSr2Mn2O7, can be manipulated using ultrafast optical excitation. The time-dependent evolution of the Jahn-Teller superlattice reflection, the indicator of the formation of charge and orbital order, was measured at different laser fluences. The laser-induced change in the Jahn-Teller reflection intensity shows a reversal of sign between earlier (∼10 ns) and later (∼150 ns) times during the relaxation of the sample. This is consistent with a physics picture whereby the laser excitation modulates the local competition between the metallic and the insulating phases.

We describe recent results in quantum materials through the use of a new tool: the x-ray free electron laser. We briefly describe the instrument and x-ray source capabilities and then discuss how this tool can bring new insights into materials with strong-electron correlations by ultrafast x-ray scattering from electronic structure.

Systems with a single or several coupled electron spins are commonly described with the quantum approach while ferromagnetic domains with millions of coupled spins are classical systems. Large spin clusters and superparamagnetic nanoparticles contain hundreds of coupled electron spins, and are on the boundary between classical and quantum behavior. Electron magnetic resonance observed in ultra-fine iron oxide nanoparticles (∼ 5 nm size) reveals several features which are typical for paramagnetic spins and absent in macroscopic systems, including multiple quantum transitions observed at H0/n, where n = 2, 3, 4 and H0 is the field of the main resonance. In order to better understand the transition from quantum to classical behavior and magnetization dynamics at the nanoscale, we study the evolution of the EMR signal with increase of the particle size in suspensions of magnetite nanoparticles. The experimental data are compared with numerical simulations.

Multiferroic BFO/SRO/Si trilayers have been prepared by pulsed laser deposition in the form of thin films. As a function of the BFO layer thickness, magnetic and magneto-transport properties have been investigated at room temperature and down to 5 K. At low BFO layer thickness, a residual γ-Fe2O3 phase, which interacts interfacially with the SRO and BFO layers, is responsible for moderately hard magnetic properties of the film. On increasing BFO layer thickness, more homogeneous deposits are obtained with uniform magnetic and magneto-resistive properties.

We report magneto-dielectric anomaly of the multiferroic (Bi0.95Nd0.05)(Fe0.97Mn0.03)O3 (BNFM) ceramic near Néel temperature. The ceramic pellets were synthesized by conventional solid state reaction route. X-ray diffraction patterns revealed that most of the peaks shifted slightly towards higher Bragg’s angle compared to those of pure BiFeO3 and also confirmed the formation of rhombohedral phase. It also suggests that the small chemical substitution of Nd and Mn atoms at Bi and Fe sites of BiFeO3 (BFO) perovskite respectively does not alter the crystal structure. Temperature and frequency dependent dielectric response indicate large dielectric anomaly at 620 K, slightly below the known Néel temperature of BFO. The enhancement in dielectric properties of BNFM ceramic was observed as compared to BFO due to suppression of oxygen vacancies by the doping. Temperature dependent dielectric response in conjunction with Raman and thermo-analytical data show that the BNFM sample presents significant magneto-dielectric response around Néel temperture TN ∼ 620 K.