scholarly journals Magnetic ordering and fluctuation in Kagome lattice anti-ferromagnets, Fe and Cr jarosites

2001 ◽  
Vol 79 (11-12) ◽  
pp. 1511-1516 ◽  
Author(s):  
M Nishiyama ◽  
T Morimoto ◽  
S Maegawa ◽  
T Inami ◽  
Y Oka
Keyword(s):  
Magnetic Transition ◽  
Magnetic Ordering ◽  
Exchange Interactions ◽  
Lattice Relaxation ◽  
Spin Correlation ◽  
Spin Lattice Relaxation ◽  
Kagome Lattice ◽  
Kagomé Lattice ◽  
Spin Lattice ◽  
High Temperature Expansion

Jarosite family compounds, KFe3(OH)6(SO4)2 (abbreviated to Fe jarosite) and KCr3(OH)6(SO4)2 (Cr jarosite) are typical examples of Heisenberg anti-ferromagnets on the Kagome lattice and have been investigated by means of magnetization and NMR experiments. The susceptibility of Cr jarosite deviates from the Curie–Weiss law due to the short-range spin correlation below about 150 K and shows the magnetic transition at 4.2 K, while Fe jarosite has the transition at 65 K. The measured susceptibility fits well with the calculated one on the high-temperature expansion for the Heisenberg anti-ferromagnet on the Kagome lattice. The values of the exchange interactions of Cr jarosite and Fe jarosite are derived to be JCr = 4.9 K and JFe = 23 K, respectively. The 1H-NMR spectra of Fe jarosite suggest that the ordered spin structure is the q = 0 type 120° configuration with +1 chirality. The transition is considered to be caused by a weak single-ion type anisotropy. The spin-lattice relaxation rate, 1/T1, of Fe jarosite in the ordered phase decreases sharply with decreasing temperature and can be well explained by the two-magnon process of spin wave with the anisotropy. PACS No.: 75.25+z

A 35Cl NQR Study on Exchange Interactions between Paramagnetic [IrCl6]2– Ions

2002 ◽  
Vol 57 (6-7) ◽  
pp. 431-434 ◽  
Author(s):  
Hiroshi Miyoshi ◽  
Keizo Horiuchi ◽  
Ryuichi Ikeda
Keyword(s):  
Relaxation Times ◽  
Exchange Interactions ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
35Cl Nqr ◽  
Temperature Dependences ◽  
Field Fluctuations ◽  
Paramagnetic Ions ◽  
Exchange Parameters

The 35Cl and 37Cl NQR frequencies and spin-lattice relaxation times T1Q in paramagnetic M2IrCl6 (M = NH4, Cs) were measured at 4 - 350 K. The observed temperature dependences were attributed to EFG fluctuations caused by lattice vibrations and magnetic field fluctuations caused by paramagnetic ions. The exchange parameters in the NH4 and Cs salts were calculated from 35Cl NQR T1Q to be 8.6 K and 1.8 K respectively. 37Cl data yielded 9.1 K and 2.1 K respectively. The obtained lattice constant dependence of J values was explained by considering Ir-Cl Cl-Ir superexchange interaction

Superconductivity and Magnetic Properties of the t–J Model of Cuprate Perovskites

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3039-3041
Author(s):  
A. Sherman ◽  
M. Schreiber
Keyword(s):  
Spin Echo ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Wave Theory ◽  
Spin Correlation ◽  
Quantitative Agreement ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Hole Spectrum ◽  
Temperature Dependences

We apply the spin-wave theory with the additional constraint of zero staggered magnetization to investigate the two-dimensional t–J model in the paramagnetic state in the ranges of hole concentrations 0.02 ≲ x ≲ 0.17 and temperatures T ≲ 100 K. In this region the hole spectrum is nonmetallic and contains a pseudogap with properties similar to those observed in Bi2212 photoemission. The calculated spin correlation length, susceptibility, spin-lattice relaxation times at the Cu and O sites and Cu spin-echo decay time are in qualitative and in some cases in quantitative agreement with experiment in underdoped YBa2Cu3O 6+y. The temperature dependences of these quantities are typical for the quantum disordered regime with a pseudogap in the spectrum of magnetic excitations. In the Eliashberg formalism the hole–magnon interaction was found to be unable alone to give rise to superconductivity. With inclusion of a moderate interaction with apex oxygen vibrations, high-T c 's are obtained for even frequency dx2-y2 pairing.

scholarly journals Magnetic Properties of the Doped Two-Dimensional Antiferromagnet

2003 ◽  
Vol 17 (10n12) ◽  
pp. 433-440 ◽  
Author(s):  
A. Sherman ◽  
M. Schreiber
Keyword(s):  
Magnetic Properties ◽  
Hole Concentration ◽  
Low Frequency ◽  
Lattice Relaxation ◽  
Spin Correlation ◽  
The Self ◽  
Spin Lattice Relaxation ◽  
Two Dimensional ◽  
Spin Lattice ◽  
Consistent Solution

The variety of the normal-state magnetic properties of cuprate high-Tc superconductors is interpreted based on the self-consistent solution of the self-energy equations for the two-dimensional t-J model. The observed variations of the spin correlation length with the hole concentration x, of the spin susceptibility with x and temperature T and the scaling of the static uniform susceptibility are well reproduced by the calculated results. The nonmonotonic temperature dependence of the Cu spin-lattice relaxation rate is connected with two competing tendencies in the low-frequency susceptibility: its temperature decrease due to the increasing spin gap and the growth of the susceptibility in this frequency region with the temperature broadening of the maximum in the susceptibility.

SPIN DENSITY WAVE ORDER AND FLUCTUATIONS IN (TMTSF)2PF6 AT VERY HIGH MAGNETIC FIELDS

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3252-3257 ◽  
Author(s):  
W. G. CLARK ◽  
P. VONLANTHEN ◽  
A. GOTO ◽  
K. B. TANAKA ◽  
B. ALAVI ◽  
...  
Keyword(s):  
Spin Density ◽  
Magnetic Transition ◽  
Density Wave ◽  
Spin Density Wave ◽  
Field Measurements ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Sharp Change ◽  
Spin Lattice

We report extremely high field and frequency NMR measurements of the proton spin-lattice relaxation rate (1/T1) in (TMTSF)2PF6. They probe the spin density wave (SDW) fluctuations in the critical regime near the SDW transition and in the ordered phase at lower temperatures. The highest field measurements were made using the NHMFL hybrid magnet at 44.7 T and a proton NMR frequency of 1.9 GHz. A quadratic increase in the transition temperature is observed that agrees with transport measurements made at lower fields. As the field is increased above 40 T, a change in the SDW critical dynamics is seen. Also, the behavior of 1/T1 vs. the alignment of the magnetic field suggests a magnetic transition at moderate to high fields with the characteristics of a sharp change in the orientation of the SDW polarization, but with parameters that differ from the spin-flop transition seen at low field.

NQR AND NMR STUDIES OF YBa2Cu3Ox(6.0 ≦ x ≦ 6.91)

1989 ◽  
Vol 03 (01) ◽  
pp. 93-95 ◽  
Author(s):  
TAKASHI IMAI ◽  
TADASHI SHIMIZU ◽  
HIROSHI YASUOKA ◽  
YUTAKA UEDA ◽  
KOJI KOSUGE
Keyword(s):  
Temperature Dependence ◽  
Magnetic Ordering ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Fluctuations ◽  
Spin Lattice Relaxation ◽  
Nmr Studies ◽  
Oriented Sample ◽  
Spin Lattice ◽  
Anisotropic Superconductivity

Nuclear Quadrupole Resonance (NQR) and Nuclear Magnetic Resonance (NMR) have been utilized to investigate the 90 K class superconductor YBa 2 Cu 3 O 6.91 and relevant oxides YBa 2 Cu 3 O x(6.0 ≦ x ≦ 6.91). Two 63 Cu NQR lines have been observed at about 31 MHz and 22 MHz for x = 6.91, which were proved to be from the Cu2 and Cu1 sites respectively using the NMR technique for an oriented sample. The spin-lattice relaxation time T1 exhibits anomalous temperature dependence with high relaxation rate in the normal state. Power-law like temperature dependence was observed well below T c for the Cu2 sites. The former indicates the strong influence of Cu spin fluctuations, while the latter may be understood as the realization of the anisotropic superconductivity. Antiferromagnetic nuclear resonance has been obtained for x = 6.0 yielding a clear evidence of magnetic ordering in the Cu2-O 2 planes. This is consistent with neutron scattering and μ SR studies.

63/65Cu- NQR Study of impurity-lnduced Magnetic Order in YBa2(Cu1-xMx)3O7 (M = Fe, Co)

1990 ◽  
Vol 45 (3-4) ◽  
pp. 423-428 ◽  
Author(s):  
Y. Nakamichi ◽  
K. Kumagai ◽  
H. Nakajima ◽  
T. Fujita
Keyword(s):  
Relaxation Rate ◽  
Low Temperatures ◽  
Magnetic Order ◽  
Magnetic Ordering ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice Relaxation Rate ◽  
Spin Lattice ◽  
System A ◽  
Magnetic Ions

Abstract We have studied 63/65 Cu NQR at the Cu(l)-chain and Cu(2)-plane site of YBa2(Cu1-x Mx)3O7 (M = Fe, Co). The spin-lattice relaxation rate, T1-1 , is enhanced at low temperatures and has in the Fe-system a peak at 2 and 4 K for x = 0.005 and 0.015, respectively. Below the peak temperatures the intensity of the Cu-NQR signal decreases rapidly. The results suggest that magnetic ordering of either Fe or Cu moments occurs without destroying the superconductivity below Tc on substituting Cu by magnetic ions.

Anisotropic 2H-NMR spin-lattice relaxation in oriented bilayers of DMPC and DMPC + cholesterol

1992 ◽  
Vol 89 ◽  
pp. 237-242 ◽  
Author(s):  
MA Krajewski-Bertrand ◽  
Y Nakatani ◽  
G Ourisson ◽  
EJ Dufourc ◽  
A Milon
Keyword(s):  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
2H Nmr ◽  
Spin Lattice
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