Cu spin dynamics in the overdoped regime ofLa2−xSrxCu1−y

Risdiana Risdiana

¹

,

Tadashi Adachi

²

,

N. Oki

³

et al.

Abstract

Muon-spin-relaxation measurements have been performed for partially Zn-substituted La 2−x Sr x Cu 1−y Zn y O 4 with y = 0 -0.10 in the overdoped regime up to x = 0.30. In the 3% Zn-substituted samples up to x = 0.27, exponential-like depolarization of muon spins has been observed at low temperatures, indicating a Zn-induced slowing down of the Cu spin fluctuations. The depolarization rate decreases with increasing x, and almost no fast depolarization of muon spins has been observed for x = 0.30 where superconductivity disappears. The present results suggest that there is no quantum critical point at x ϳ 0.19. These results are discussed in terms of the stripe-pinning model and the phase-separation model.

Distinct Fe-induced magnetic states in the underdoped and overdoped regimes of La2−xSrxCu<

“…Moreover, the static magnetic order appears through the Fe substitution even in the overdoped regime where no development of the magnetic correlation is observable in LSCO from µSR measurements. [11,12] On the other hand, the suppression of superconductivity by the Fe substitution is larger than by the Zn substitution especially in the underdoped regime. Given the large magnetic moment of Fe, this evokes conventional superconductors based on the BCS theory [46] where T c is depressed by magnetic impurities more than by nonmagnetic impurities.…”

“…3, (iii) the large T N values in spite of the magnetic correlation weakened with hole doping, (iv) the marked enhancement of T N by the Fe substitution, and (v) the robust high T c values in spite of the large T N values. Supposed the stripe-pinning effect by Zn in overdoped LSCZO, [12] the stripes are probably disordered due to excess holes overflowing into the spin domain and therefore causing a disorder in the magnetic state. This is consistent with the absence of muon-spin precession.…”

“…2(a). That is, it is found that the LF spectra shift in parallel up to 3500 Oe, which is a typical [10][11][12]23] All the spectra are shown after subtracting the background from the raw spectra and being normalized by the value of the asymmetry at t = 0. Solid lines indicate the best-fit results using A(t) = A0e …”

“…RESULTS Figure 1 shows the ZF-µSR time spectra of Fesubstituted LSCFO with y = 0.005 and 0.01 in a wide range of p. For comparison, ZF-µSR spectra of impurityfree LSCO and 1% Zn-substituted La 2−x Sr x Cu 1−y Zn y O 4 (LSCZO) with y = 0.01 formerly obtained by our group are also shown. [10][11][12]23] Here, p is defined as p = x − y for LSCFO due to the substitution of trivalent Fe 3+ for divalent Cu 2+ and as p = x for LSCO and LSCZO. All the spectra are shown after subtracting the background from the raw spectra and being normalized by the value of the asymmetry at t = 0.…”

“…In the case of the substitution of nonmagnetic Zn, muon-spin-relaxation (µSR) measurements have suggested that dynamical stripe correlations tend to be pinned by Zn and statically stabilized in the underdoped and optimally doped regimes of HTSC. [8][9][10][11] Moreover, the magnetic correlation has been found to be developed by the Zn substitution in the overdoped regime of LSCO, [11,12] Bi 2 Sr 2 Ca 1−x Y x Cu 2 O 8+δ , [13,14] YBa 2 Cu 3 O 7−δ (YBCO), [15,16] and Bi 1.74 Pb 0.38 Sr 1.88 CuO 6+δ . [17] Elastic neutron-scattering measurements in underdoped and optimally doped LSCO have also revealed that the incommensurate magnetic order is induced by the Zn substitution.…”