Relaxation Anomalies of69/71Ga NQR in the Paramagnetic State of the Itinerant Antiferromagnet UGa3: Possible Evidence for a Crossover to Localized Spin Fluctuations and Development of Orbital Fluctuations of 5f-electrons at High Temperatures

2004 ◽  
Vol 73 (2) ◽  
pp. 469-474 ◽  
Author(s):  
Shigeru Takagi ◽  
Hideaki Muraoka ◽  
Tatsuma D. Matsuda ◽  
Yoshinori Haga ◽  
Shinsaku Kambe ◽  
...  
Keyword(s):  
High Temperatures ◽  
Paramagnetic State ◽  
Spin Fluctuations ◽  
5F Electrons

SUPPRESSION OF SPIN FLUCTUATIONS IN YMn2 BY HYDROSTATIC PRESSURE

1993 ◽  
Vol 07 (01n03) ◽  
pp. 826-829 ◽  
Author(s):  
E. BAUER ◽  
I.S. DUBENKO ◽  
E. GRATZ ◽  
R. HAUSER ◽  
A. MARKOSYAN ◽  
...  
Keyword(s):  
Hydrostatic Pressure ◽  
Neutron Diffraction ◽  
Pressure Dependence ◽  
Ambient Pressure ◽  
Paramagnetic State ◽  
Spin Fluctuations ◽  
Interatomic Distances ◽  
Effective Moment ◽  
Large Pressure ◽  
Phase Compound

The cubic Laves phase compound YMn2 exhibits a huge spontaneous volume magnetostriction at the Néel temperature (TN=100 K). The magnetic moment per Mn atom is 2.7 μB at 2 K. From polarized neutron diffraction in the paramagnetic state it has been shown that the effective moment persisting above TN is reduced (1.6 μB at 120 K). The anomalously large pressure dependence of TN (dTN/dp=–35 K/kbar) is an evidence for the sensitive role played by the Mn—Mn interatomic distances. In the paramagnetic state, the influence of spin fluctuations dominates the physical properties. We have studied the effect of pressure on the resistivity up to 16 kbar. From dρ/dT we have estimated the spinfluctuation temperature as a function of pressure. The value at ambient pressure is 15 K which is in agreement with that determined in the paramagnetic Y0.9Lu0.1Mn2 compound.

scholarly journals Spin fluctuations of the uranium 5f-electrons in UN according to 14N-NMR data

2019 ◽  
Vol 1389 ◽  
pp. 012082
Author(s):  
Vasily V Ogloblichev ◽  
Stanislav V Verkhovskii ◽  
Aleksey M Potapov ◽  
Aleksandr Yu Germov ◽  
Almaz F Sadykov
Keyword(s):  
Spin Fluctuations ◽  
Nmr Data ◽  
5F Electrons ◽  
14N Nmr

Effect of Pressure on the Spin Fluctuations and the Helical Ferromagnetism of MnSi

2016 ◽  
Vol 257 ◽  
pp. 30-33
Author(s):  
Aleksandr A. Povzner ◽  
Arkadij G. Volkov ◽  
Ivan A. Yasyulevich
Keyword(s):  
Magnetic Susceptibility ◽  
Local Minimum ◽  
Spin Fluctuation ◽  
Magnetic Moments ◽  
Paramagnetic State ◽  
Spin Fluctuations ◽  
Temperature Dependent ◽  
Effect Of Pressure ◽  
Fluctuation Effects ◽  
Moriya Interaction

The effect of pressure on the Neel temperature (TN) and on the temperature dependence of the magnetic susceptibility of a helicoidal ferromagnetic MnSi was analyzed as part of the LDA+U-model augmented with the account of the relativistic antisymmetric Dzyaloshinskii-Moriya interaction. It was shown that the Fermi level is in the area of DOS local minimum. This causes instability of magnetic solutions and the occurrence of higher amplitude zero spin fluctuations simulating the pattern of local magnetic moments. An increase in temperature-dependent spin-fluctuation effects with an increase in pressure leads to a decrease in TN. As a result, at pressures above 14.45 kbar, zero spin fluctuations are retained over the entire temperature range below TN. After disappearance of helicoidal ferromagnetism, a paramagnetic state occurs where the effect of the abrupt suppression of local magnetic moments takes place upon a temperature increase.

LOW-TEMPERATURE SPECIFIC HEAT OF YMn2 IN THE PARAMAGNETIC AND ANTIFERROMAGNETIC PHASES

1993 ◽  
Vol 07 (01n03) ◽  
pp. 830-833 ◽  
Author(s):  
R.A. FISHER ◽  
R. BALLOU ◽  
J.P. EMERSON ◽  
E. LELIEVRE-BERNA ◽  
N.E. PHILLIPS
Keyword(s):  
Low Temperature ◽  
Specific Heat ◽  
Applied Pressure ◽  
Paramagnetic State ◽  
Linear Term ◽  
Spin Fluctuations ◽  
Spin Frustration ◽  
Magnetic Instability ◽  
Low Temperature Specific Heat

The low-temperature specific heat of YMn2 has been measured at applied pressures of 0 to 7.7 kbar. A paramagnetic state is stabilized for moderate values of the applied pressure (of the order of 1.6 kbar). A large linear term in the specific heat, which decreases regularly with increasing pressure, is observed in this phase. It is ascribed to giant spin fluctuations associated with a magnetic-non magnetic instability and a strong geometrical spin frustration.

scholarly journals Концентрационные флуктуации в киральных ферромагнетиках Fe-=SUB=-x-=/SUB=-Mn-=SUB=-1-x-=/SUB=-Si во внешнем магнитном поле

2020 ◽  
Vol 62 (5) ◽  
pp. 776
Author(s):  
А.А. Повзнер ◽  
А.Г. Волков ◽  
Т.М. Нуретдинов
Keyword(s):  
Magnetic Moments ◽  
Zero Point ◽  
Quantum Spin ◽  
Paramagnetic State ◽  
Spin Fluctuations ◽  
Local Magnetization ◽  
Virtual Crystal Approximation ◽  
Spin Correlations ◽  
Dynamic Spin ◽  
Chaotic Distribution

In the framework of the theory of spin fluctuations, magnetic h-T diagrams of chiral helicoidal ferromagnets FexMn1-xSi with the Dzyaloshinskii-Moriya interaction are investigated. A specific analysis of the equations of magnetic state is carried out on the basis of a model of the electronic structure following from the LDA + U + SO DOS calculations in the virtual crystal approximation. It was shown that in the concentration range x <0.12, the Fermi level remains within the local minimum DOS. In this case, a helicoidal long-range order is realized, which undergoes a first-order transition induced by spin fluctuations, accompanied by the formation of intermediate skyrmion phases induced by an external magnetic field. With increasing x arising due to the chaotic distribution of the magnetic moments of manganese and iron over the nodes, the effects of concentration fluctuations suppress zero-point quantum spin fluctuations. In this case, the condition for the appearance of skyrmion phases is violated for x> 0.12, and the region of the helicoidal ferromagnetic order is preserved up to concentrations xc = 0.20. In the interval 0.10 <x <0.20, the transition induced by fluctuations to the paramagnetic state is accompanied by the disappearance of local magnetization and the formation of a paramagnetic state with dynamic spin correlations.

Spin Polarons at High Temperatures in Undoped Lanthanum Manganites

2010 ◽  
Vol 168-169 ◽  
pp. 473-476
Author(s):  
T.I. Arbuzova ◽  
Sergey V. Naumov ◽  
Natalia V. Kostromitina
Keyword(s):  
Magnetic Properties ◽  
Curie Temperature ◽  
Cell Volume ◽  
High Temperatures ◽  
Unit Cell Volume ◽  
Paramagnetic State ◽  
Unit Cell ◽  
Temperature Range ◽  
Lanthanum Manganites ◽  
Spin Polarons

Magnetic properties of undoped samples of lanthanum manganites in the temperature range 77-650K are reported. The ferromagnetic Curie temperature increases when the unit-cell volume decreases and the number of cation defects increases. Uncorrelated polarons and noninteracting moments of Mn ions are present in the region TC < T < 440K. Above 2TC < 440 K < T, the nonstoihiometric LaMnO3 compound passes into the homogeneous paramagnetic state.

Spin Fluctuations in Pressure-Induced Paramagnetic State of YMn2 — Comparison with High-Tc Cuprates —

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3345-3348
Author(s):  
G. -G. Zheng ◽  
K. Nishikido ◽  
Y. Kitaoka ◽  
K. Asayama ◽  
R. Hauser
Keyword(s):  
Correlation Length ◽  
Paramagnetic State ◽  
Spin Fluctuations ◽  
High Tc ◽  
Magnetic Correlation ◽  
High Tc Cuprates

From our NMR measurements, we compare the spin fluctuations spectrum in high-T c cuprates and the pressure-induced paramagnetic state of YMn 2. It is pointed out that the latter has a shorter magnetic correlation length and the bandwidth is smaller by one order in magnitude than the former.

In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

1991 ◽  
Vol 49 ◽  
pp. 660-661
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
High Temperatures ◽  
Image Resolution ◽  
Atomic Processes ◽  
Crystal Surfaces ◽  
Beam Radiation ◽  
Surface Areas ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

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