Naslov
The in- and out-of-plane magnetisation of highly underdoped YBa2Cu3O6+x single crystals

Autori
Kokanović, Ivan ; Cooper, John

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Skup
20th INTERNATIONAL CONFERENCE ON MAGNETISM

Mjesto i datum
Barcelona, Španjolska, 05.07.2015. - 10.07.2015

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Superconductivity, Magnetic properties, Strongly correlated systems

Sažetak
In two recent papers [1, 2] we have shown how measurements of static magnetic susceptibility c(T) of YBa2Cu3O6+x single crystals for magnetic fields applied along the c-axis, and ab(T) for fields in the ab-plane, can give useful information about their thermodynamic properties which are still being hotly debated. SQUID magnetometry above the superconducting (s/c) transition temperature Tc is used for larger crystals, while piezolever torque magnetometry gives c(T)-ab(T) for tiny crystals [2]. We briefly review the main results of this work - the T-dependent anisotropy well above Tc arises from the pseudogap and the g-factor anisotropy, while at lower T there are Gaussian s/c fluctuations with a strong cut-off above 1.1 Tc. We then present some new data for heavily under-doped crystals with hole concentrations per CuO2 plane, p =0.058 to 0.073. This is the region where neutron scattering studies [3, 4] give evidence for competition between incommensurate magnetic short-range order and superconductivity. We have studied crystals with three values of x, measuring c(T) and ab(T) immediately after fixing x by quenching on to a copper block and again after allowing sufficient time at room temperature for the Cu-O chains to order. We thus have data for three pairs of underdoped (UD) crystals with Tc ranging from 13 to 36 K, namely UD13 and UD20, UD15 and UD30, UD23 and UD36. As found previously for polycrystalline samples [5] ordering the Cu-O chains increases Tc and substantially reduces the Curie term. In contrast to the Pauli-like susceptibility from the CuO2 planes, the Curie terms are isotropic. Plots of c(T) vs. ab(T) give an unexpected result, the Curie terms disappear above a p-dependent onset temperature TCurie of order 200 K. For all six samples D(T)=c(T)ab(T) has a weakly T-dependent linear region at higher T where D(0) is 1-2 x10-4emu/mol. We have discussed deviation from this linear behavior in terms of 2D or 3D Gaussian superconducting fluctuations. [1] I. Kokanović, et al., Europhys. Lett. 98, 57011 (2012). [2] I. Kokanović, et al., Phys. Rev. B 88, 060505(R) (2013). [3] D. Haug, et al., Phys. Rev. Lett. 103, 017001 (2009). [4] D. Haug, et al., New J. Phys. 12, 105006 (2010). [5] T. Wu, et al., Nature 477, 191 (2011).

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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