Superconductor antiferromagnetic

The development of neutron diffraction by C G Shull and coworkers [30] led to the detennination of the existence, previously only a hypothesis, of antiferromagnetism and ferrimagnetism. More recently neutron diffraction, because of its sensitivity to light elements in the presence of heavy ones, played a cmcial role in demonstrating the importance of oxygen content m high-temperature superconductors. 

Although erbium is magnetic at very low temperatures, it is antiferromagnetic and becomes a superconductor at temperatures near absolute zero. It is insoluble in water but soluble in acids. Its salts range from pink to red. Erbium and some of the other rare-earth elements are considered to be impurities in the minerals in which they are found. Small quantities of erbium can also be separated from several other rare-earths. 

Figure 1.19. Generic T-P phase diagram for BFS. The origin on the pressure axis is arbitrarily set for (TMTTF)2PF6. MH, Mott-Hubbard M, Metal SP, Spin-Peierls AF, Antiferromagnetic SDW, Spin-Density-Wave SC, Superconductor. Adapted from Auban-Senzier J6rome, 2003.

Lefebvre S, Wzietek P, Brown S, Bourbonnais C, Jerome D, Meziere C, Eourmigue M, Batial P (2000) Mott transition, antiferromagnetism, and unconventional superconductivity in layered organic superconductors. Phys Rev Lett 85 5420-5423... 

Konoike T, Uji S, Terashima T, Nishimura M, Yasuzuka S, Enomoto K, Eujiwara H, Zhang B, Kobayashi H (2004) Magnetic-field-induced superconductivity in the antiferromagnetic organic superconductor K-(BETS)2peBr4. Phys Rev B70 094514/l-5... 

Takabayashi Y, Ganin AY, Jeglic P, Arcon D, Takano T, Iwasa Y, Ohishi Y, Takata M, Takeshita N, Prassides K, Rosseinsky MJ (2009) The disorder-free non-BCS superconductor CS3C60 emerges from an antiferromagnetic insulator parent state. Science 323 1585-1590... 

In what follows we should bear in mind that the generation of a diamagnetic metallic state (irrespective of whether it is a superconductor or not) will not be favored by a half-filled band of electrons. Either a Peierls distortion or the generation of an antiferromagnetic insulating state will result, with a ferromagnet being less likely for the reasons discussed. Superconductivity in these materials is in fact only observed if electrons are removed, or (less commonly to date) added to the half-filled band. Considerable effort is underway to theoreti-... 

An unusual feature of the cuprate superconductors is the anomalous suppression of superconductivity in La2 Ba Cu04 and related phases when the hole concentration X is near 1/8. A possible explanation is a dynamical modulation of spin and charge giving antiferromagnetic stripes of copper spins periodically separated from the domains of holes. Neutron-diffraction evidence has been presented in the case of Laj g Nd() Sr CuO (x = 0.12) which is a static analogue of the dynamical stripe model (Tranquada et al., 1995). It appears that spatial modulations of spin and charge density are related to the superconductivity in these oxides. 

Which sort of transition is occurring in the new superconductors, such as the antiferromagnetic insulator La2 xSrxCu04 for small x, will be discussed in Chapter 9. 

In the Heusler alloy ErPd2Sn superconductivity and antiferromagnetic order coexist although there is no clear separation between the superconducting and the magnetic sublattices and Tc 1.17 K is not much different from 7 n 1 K (Shelton et al. 1986 Stanley et al. 1987). However, the focus on this interesting compound was short lived because of the discovery of the high Tc cuprate superconductors (Lynn 2001). 

An interesting theoretical prediction is that, similar as in the p-wave superconductors discussed in the next subsection, non-magnetic impurities in an antiferromagnetic superconductor cause pair breaking (Morozov 1980 Zwicknagl and Fulde 1981) whereas non-magnetic impurities in a non-magnetic superconductor are not expected to destroy superconductivity (Anderson 1959). 

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