TY - JOUR
T1 - Anisotropy and critical current density of MgB2 thin films grown in-situ by molecular beam epitaxy
AU - Jo, W.
AU - Beasley, M. R.
AU - Hammond, R. H.
N1 - Funding Information:
Manuscript received August 5, 2002. This work was supported by the Air Force Office of Scientific Research under Grant F49620-01-0103. The authors are with Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305-4045 USA (e-mail: wmjo@stanford.edu; beasley@stanford.edu; rhammond@stanford.edu). Digital Object Identifier 10.1109/TASC.2003.812216
PY - 2003/6
Y1 - 2003/6
N2 - We report transport properties of superconducting MgB2 thin films in-situ grown by molecular beam epitaxy. The MgB2 films show a superconducting transition at 34.5 K with δTc < 1 K. We measure the in-plane electrical resistivity of the films in magnetic field to 8 T and estimate the upper critical field Hc2⊥(0) ∼ 32 T for field oriented along the c-axis and Hc2∥(0) ∼ 35 T in the plane of the film. We find the zero-temperature coherence lengths ξc(0) ∼ 31 Å and ξab(0) ∼ 36 Å, indicating the field anisotropy ratio is 1.2, comparable with reported in-situ epitaxial thin films, but less than single crystals. The calculated electronic mean free path l = 25 Å is smaller than the coherence length, which places our films in the dirty limit. Estimates of the critical current density, Jc, using magnetic field hysteresis loops and the Bean critical state model give nominal critical current densities on the order of 106 A/cm2 at 15 K and self-field.
AB - We report transport properties of superconducting MgB2 thin films in-situ grown by molecular beam epitaxy. The MgB2 films show a superconducting transition at 34.5 K with δTc < 1 K. We measure the in-plane electrical resistivity of the films in magnetic field to 8 T and estimate the upper critical field Hc2⊥(0) ∼ 32 T for field oriented along the c-axis and Hc2∥(0) ∼ 35 T in the plane of the film. We find the zero-temperature coherence lengths ξc(0) ∼ 31 Å and ξab(0) ∼ 36 Å, indicating the field anisotropy ratio is 1.2, comparable with reported in-situ epitaxial thin films, but less than single crystals. The calculated electronic mean free path l = 25 Å is smaller than the coherence length, which places our films in the dirty limit. Estimates of the critical current density, Jc, using magnetic field hysteresis loops and the Bean critical state model give nominal critical current densities on the order of 106 A/cm2 at 15 K and self-field.
KW - Anisotropy of coherence length
KW - Critical current density
KW - In-situ growth
KW - MgB thin films
KW - Molecular beam epitaxy
UR - http://www.scopus.com/inward/record.url?scp=0042475494&partnerID=8YFLogxK
U2 - 10.1109/TASC.2003.812216
DO - 10.1109/TASC.2003.812216
M3 - Conference article
AN - SCOPUS:0042475494
SN - 1051-8223
VL - 13
SP - 3257
EP - 3260
JO - IEEE Transactions on Applied Superconductivity
JF - IEEE Transactions on Applied Superconductivity
IS - 2 III
Y2 - 4 August 2002 through 9 August 2002
ER -