Magnetic Order and Structure of Ultrathin Films and Multilayers

1991 ◽  
Vol 232 ◽  
Author(s):  
G. Lugert ◽  
G. Bayreuther ◽  
S. Lehner ◽  
G. Gruber ◽  
P. Bruno
Keyword(s):  
Ground State ◽  
Ultrathin Films ◽  
Film Formation ◽  
Epitaxial Films ◽  
Spin Fluctuations ◽  
Superparamagnetic Relaxation ◽  
3 Dimensional ◽  
Spin Excitations ◽  
Ferromagnetic Ground State ◽  
Dimensional Growth

ABSTRACTUltrathin epitaxial films grown in UHV – Fe(110) on Au(111) and Ag(111), Co(0001) on Au(111) – , sputtered Fe films between Ag and sputtered Fe/Au multilayers were studied by SQUID magnetometry and Mössbauer spectroscopy (CEMS). It could be shown that the magnetic anisotropy relative to the film normal, the, ground state magnetic moment per Fe atom and thermal spin excitations are affected by the structure of the films. In particular, a more 3-dimensional growth mode in the early state of film formation which is observed except in a certain temperature range around 300 K reduces the apparent magnetic interface anisotropy and the ferromagnetic ground state moment, and it enhances the thermal spin fluctuations and the tendency for superparamagnetic relaxation in the thinnest films.

SUPPRESSION OF THE FERROMAGNETIC STATE BY DISORDER IN THE KONDO LATTICE

1992 ◽  
Vol 06 (21) ◽  
pp. 1329-1334 ◽  
Author(s):  
M. CRIŞAN ◽  
C. POPOVICIU
Keyword(s):  
Ground State ◽  
Fermi Liquid ◽  
Ferromagnetic State ◽  
Kondo Lattice ◽  
Spin Fluctuations ◽  
Low Concentration ◽  
Conduction Electrons ◽  
Ferromagnetic Ground State

The ferromagnetic ground state of a Kondo lattice with a low concentration of conduction electrons is ferromagnetic. Assuming the existence of disorder in the Fermi liquid of the conduction electrons we showed that the ferromagnetic state can be suppressed by the effect of the spin fluctuations of the disordered Fermi liquid.

Epitaxial growth manner and structure of superconducting oxide films

1990 ◽  
Vol 48 (4) ◽  
pp. 2-3
Author(s):  
Yoshichika Bando ◽  
Takahito Terashima ◽  
Kenji Iijima ◽  
Kazunuki Yamamoto ◽  
Kazuto Hirata ◽  
...  
Keyword(s):  
Ultrathin Films ◽  
Film Surface ◽  
High Energy ◽  
Epitaxial Films ◽  
Layer By Layer ◽  
Initial Growth ◽  
In Situ Growth ◽  
High Quality ◽  
Activated Reactive Evaporation

The high quality thin films of high-Tc superconducting oxide are necessary for elucidating the superconducting mechanism and for device application. The recent trend in the preparation of high-Tc films has been toward “in-situ” growth of the superconducting phase at relatively low temperatures. The purpose of “in-situ” growth is to attain surface smoothness suitable for fabricating film devices but also to obtain high quality film. We present the investigation on the initial growth manner of YBCO by in-situ reflective high energy electron diffraction (RHEED) technique and on the structural and superconducting properties of the resulting ultrathin films below 100Å. The epitaxial films have been grown on (100) plane of MgO and SrTiO, heated below 650°C by activated reactive evaporation. The in-situ RHEED observation and the intensity measurement was carried out during deposition of YBCO on the substrate at 650°C. The deposition rate was 0.8Å/s. Fig. 1 shows the RHEED patterns at every stage of deposition of YBCO on MgO(100). All the patterns exhibit the sharp streaks, indicating that the film surface is atomically smooth and the growth manner is layer-by-layer.

scholarly journals Evolution of spin excitations from bulk to monolayer FeSe

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jonathan Pelliciari ◽  
Seher Karakuzu ◽  
Qi Song ◽  
Riccardo Arpaia ◽  
Abhishek Nag ◽  
...  
Keyword(s):  
Quantum Monte Carlo ◽  
Spin Dynamics ◽  
Spin Fluctuations ◽  
Superconducting Transition ◽  
Pairing Mechanism ◽  
Range Magnetic Order ◽  
X Ray Scattering ◽  
Spin Excitations ◽  
Order Of Magnitude ◽  
Long Range Magnetic Order

AbstractIn ultrathin films of FeSe grown on SrTiO3 (FeSe/STO), the superconducting transition temperature Tc is increased by almost an order of magnitude, raising questions on the pairing mechanism. As in other superconductors, antiferromagnetic spin fluctuations have been proposed to mediate SC making it essential to study the evolution of the spin dynamics of FeSe from the bulk to the ultrathin limit. Here, we investigate the spin excitations in bulk and monolayer FeSe/STO using resonant inelastic x-ray scattering (RIXS) and quantum Monte Carlo (QMC) calculations. Despite the absence of long-range magnetic order, bulk FeSe displays dispersive magnetic excitations reminiscent of other Fe-pnictides. Conversely, the spin excitations in FeSe/STO are gapped, dispersionless, and significantly hardened relative to its bulk counterpart. By comparing our RIXS results with simulations of a bilayer Hubbard model, we connect the evolution of the spin excitations to the Fermiology of the two systems revealing a remarkable reconfiguration of spin excitations in FeSe/STO, essential to understand the role of spin fluctuations in the pairing mechanism.

scholarly journals Investigation of a Structural Phase Transition and Magnetic Structure of Na2BaFe(VO4)2: A Triangular Magnetic Lattice with a Ferromagnetic Ground State

2017 ◽  
Vol 56 (24) ◽  
pp. 14842-14849 ◽  
Author(s):  
Liurukara D. Sanjeewa ◽  
Vasile O. Garlea ◽  
Michael A. McGuire ◽  
Matthias Frontzek ◽  
Colin D. McMillen ◽  
...  
Keyword(s):  
Phase Transition ◽  
Magnetic Structure ◽  
Structural Phase Transition ◽  
Ground State ◽  
Structural Phase ◽  
Ferromagnetic Ground State

Surface Morphology of AlN Nucleation Layer Grown on Si by MOCVD

2015 ◽  
Vol 1120-1121 ◽  
pp. 391-395 ◽  
Author(s):  
Shu Fan ◽  
Le Yu ◽  
Xiao Long He ◽  
Ping Han ◽  
Cai Chuan Wu ◽  
...  
Keyword(s):  
Chemical Vapor ◽  
Growth Time ◽  
Organic Chemical ◽  
Nucleation Layer ◽  
Coverage Ratio ◽  
3 Dimensional ◽  
Aln Film ◽  
Metal Organic ◽  
Dimensional Growth ◽  
Organic Chemical Vapor Deposition

The AlN nucleation layer (NL) has been deposited on Si (111) substrate by metal-organic chemical vapor deposition (MOCVD). The result indicates that the growth mode of the AlN NL is in the form of 2-dimensional plane and 3-dimensional island. The proportion of 3-dimensional region increases gradually and the 2-dimensional region reduces correspondingly with the increase of growth time. The decrease of the coverage ratio of AlN grains in the 2-dimensional growth region is due to the effect of etching. AlN film with the single crystal orientation has been deposited on the optimized AlN NL.

Coherent-incoherent crossover of charge dynamics in the ferromagnetic ground state of manganites:R0.6Sr0.4MnO3(R=La-Sm)

1999 ◽  
Vol 60 (14) ◽  
pp. 10362-10366 ◽  
Author(s):  
E. Saitoh ◽  
Y. Okimoto ◽  
Y. Tomioka ◽  
T. Katsufuji ◽  
Y. Tokura
Keyword(s):  
Ground State ◽  
Charge Dynamics ◽  
Ferromagnetic Ground State

scholarly journals GGA/PBE study of the spin isomers of Fe34,40, Co23,34, and Co12Cu Clusters with Selected Geometries

2017 ◽  
Vol 56 (3) ◽  
Author(s):  
Faustino Aguilera-Granja ◽  
Andrés Vega ◽  
Luis Carlos Balbás
Keyword(s):  
Ground State ◽  
Density Functional ◽  
Energy Difference ◽  
Many Body ◽  
Generalized Gradient ◽  
Structural Isomers ◽  
Functional Theory ◽  
Ferromagnetic Ground State ◽  
Spin Isomers ◽  
Pseudo Potential

In a recent beam deflecting experiment was found that high and low spin states of pure Fe<sub>n</sub> and Co<sub>n</sub> clusters with <em>n</em> ≤ 300 atoms coexist at cryogenic temperatures. In this work we have studied the high spin (HS) and low spin (LS) states of several structural isomers of Co<sub>23</sub>, Co<sub>34</sub>, Fe<sub>34</sub>, and Fe<sub>40</sub> using the generalized gradient approximation (GGA) to density functional theory as implemented in the first-principles pseudo-potential code SIESTA. The calculated energy difference between these HS and LS isomers is not consistent with the observed coexistence, which can be due to an insufficient account of many body correlation effects in the GGA description, or to unknown isomer structures of these clusters. We have calculated within the same tools the magnetic isomers of Co<sub>12</sub>Cu cluster aimed to re-visit a former DFT prediction of an anti-ferromagnetic ground state. We find, however, a ferromagnetic ground state as expected on physical grounds. Our results exemplify the difficulties of the current DFT approaches to describe the magnetic properties of transition metal systems.

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