Effects of spin vacancies on the correlated spin dynamics in La{sub 2}Cu{ital {sub 1{minus}x}}Zn{ital {sub x}}O{sub 4} from {sup 63}Cu nuclear quadrupole resonance relaxation
- Department of Physics A. Volta, Unita INFM and Sezione INFN, Via Bassi 6, I-27100 Pavia (Italy)
{sup 63}Cu nuclear quadrupole resonance (NQR) relaxation measurements in La{sub 2}CuO{sub 4} doped Zn are used in order to investigate the temperature dependence of the in-plane magnetic correlation length {xi}{sub 2D} and the effects associated to spin vacancies in two dimensional quantum Heisenberg antiferromagnets (QHAF). The relaxation rates {ital T}{sub 1}{sup {minus}1} and {ital T}{sub 2}{sup {minus}1} have been related to the static generalized susceptibility {chi}({bold q},0) and to the decay rate {Gamma}{bold {sub q}} of the normal excitations. By using scaling arguments for {chi}({bold q},0) and {Gamma}{bold {sub q}}, the relaxation rates have been expressed in close form in terms of {xi}{sub 2D}{ital (x,T)} and its dependence on temperature and spin doping {ital x} thus extracted. The experimental findings are analyzed in light of the renormalized classical (RC) and quantum critical (QC) behaviors predicted for {xi}{sub 2D} by recent theories for {ital S}=1/2 HAF in square lattices. It is first shown that in pure La{sub 2}CuO{sub 4}, {xi}{sub 2D} is consistent with a RC regime up to about 900 K, with tendency toward the QC regime above. The spin vacancies reduce the N{acute e}el temperature according to the law {ital T{sub N}(x){approx}T{sub N}(0)(1{endash}3.5x)}. From the temperature dependence of {sup 63}Cu NQR relaxation rate {ital T}{sub 1}{sup {minus}1}, {ital T}{sub 2}{sup {minus}1} and from the composition dependence of {ital T{sub N}} it is consistently proved that the effect on {xi}{sub 2D} can be accounted for by the modification of the spin stiffness in a simple dilutionlike model, the system still remaining in the RC regime, at least for {ital T}{le}900 K. {copyright} {ital 1997 American Institute of Physics.}
- OSTI ID:
- 544311
- Report Number(s):
- CONF-961141-; ISSN 0021-8979; TRN: 97:019277
- Journal Information:
- Journal of Applied Physics, Vol. 81, Issue 8; Conference: 41. annual conference on magnetism and magnetic materials, Atlanta, GA (United States), 12-15 Nov 1996; Other Information: PBD: Apr 1997
- Country of Publication:
- United States
- Language:
- English
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