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Peak effect phenomena, surface superconductivity and paramagnetic Meissner effect in a spherical single crystal of niobium

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Title Peak effect phenomena, surface superconductivity and paramagnetic Meissner effect in a spherical single crystal of niobium
 
Creator DAS, P
TOMY, CV
TAKEYA, H
RAMAKRISHNAN, S
GROVER, AK
 
Subject nb
lattice
 
Description We have explored the vortex phase diagram in a spherical single crystal of niobium (T(c) similar to 9.3 K) via isothermal and temperature dependent dc magnetization and ac-susceptibility measurements. The crystal has extremely weak pinning that can be inferred from the reversibility of M - H loops below T(c). However, one can visualize the peak effect (PE) feature in the isothermal M - H loops up to T = 8 K. The PE is also prominent in isothermal ac-susceptibility data for H > 750 Oe. An interesting observation in the present study is the prominent fingerprints of surface superconductivity, starting just above the collapse of pinning at the peak position of the PE and ending at the surface critical field (H(c3)). We have also observed the paramagnetic Meissner effect in field-cooled magnetization data recorded at relatively large fields in this crystal. A vortex phase diagram is constructed by marking the peak positions of the PE (H(p)), the upper critical field (H(c2)) and the surface critical field (H(c3)). Unlike a previous report which shows the existence of a multi-critical point in the phase diagram of a Nb crystal, where H(p), H(c2) and H(c3) lines meet, we do not observe a multi-critical point in our weak pinning crystal.
 
Publisher IOP PUBLISHING LTD
 
Date 2011-10-22T17:40:44Z
2011-12-15T09:10:44Z
2011-10-22T17:40:44Z
2011-12-15T09:10:44Z
2009
 
Type Proceedings Paper
 
Identifier 25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 5: SUPERCONDUCTIVITY,150,-
1742-6588
http://dx.doi.org/10.1088/1742-6596/150/5/052041
http://dspace.library.iitb.ac.in/xmlui/handle/10054/14951
http://hdl.handle.net/100/1626
 
Source 25th International Conference on Low Temperature Physics (LT25),Amsterdam, NETHERLANDS,AUG 06-13, 2008
 
Language English