Paramagnetic Meissner effect in $YBa_2Cu_3O_{7-\delta}$ A non-resonant microwave absorption study

Bhat, SV and Rastogi, A and Kumar, N and Nagarajan, R and Rao, CNR (1994) Paramagnetic Meissner effect in $YBa_2Cu_3O_{7-\delta}$ A non-resonant microwave absorption study. In: Physica C, 219 (1-2). pp. 87-92.

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Abstract

The low-field dependence of non resonant microwave absorption (MWA) in polycrystalline samples of $YBa_2Cu_3O_{7-\delta}$ with $0.1\leq \delta \leq0.5$ has been measured at $T< T_c$ along with simultaneous monitoring of paramagnetic impurities in the chain copper (Cu-I) sites by EPR spectroscopy. MWA exhibits a cross-over from the normal zero-field minimum to an anomalous zero-field maximum accompanied by the gradual appearance and growth of the EPR signal as $\delta$ is changed from 0.1 to 0.5. It is to be noted that in the $\delta = 0.3-0.4$ composition range, oxygen vacancies are disordered giving rise to magnetic moments due to isolated $Cu^{2+}$ impurity iota. This correlation of the anomalous MWA with isolated paramagnetic $Cu^{2+}$ impurities is consistent with the presence of $\pi$ junctions, earlier implicated in the paramagnetic Meissner effect (PME), which in turn is related to the anomalous MWA.

Item Type: Journal Article The copyright of this article belongs to Elsevier. Division of Chemical Sciences > Solid State & Structural Chemistry UnitDivision of Physical & Mathematical Sciences > Physics 12 Jul 2006 19 Sep 2010 04:30 http://eprints.iisc.ernet.in/id/eprint/8031