Growth of (Y1−xCax)Ba2Cu4O8 in ambient pressure and its tri-axial magnetic alignment

• Published in: Superconductor science & technology 2015-08, Vol.28 (10)
• Main Authors: Horii, S, Yamaki, M, Shimoyama, J, Kishio, K, Doi, T
• Format: Article
• Language: English
• Subjects: critical temperature; irreversibility line; magnetic alignment; RE-based superconductor
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/0953-2048/28/10/105003

We report the growth of single crystals in ambient pressure and tri-axial orientation under modulated rotation magnetic fields (MRFs) for (Y1−xCax)Ba2Cu4O8 [(Y1−xCax)124] with x ≤ 0.1. Rectangular (Y1−xCax)124 crystals approximately 50 m in size have been successfully grown for x ≤ 0.1 in a growth temperature region from 650 °C to 750 °C. Their critical temperatures increased with x and exhibited approximately 91 K for x = 0.1. By applying an MRF of 10 T, pulverised powders of (Y1−xCax)124 were tri-axially aligned in epoxy resin at room temperature in a whole x region below x = 0.1. The magnitude relationship of the magnetic susceptibilities (χ) along crystallographic directions for (Y1−xCax)124 was χc > χa > χb at room temperature and was unchanged with a change in x. From changes in the degrees of the c-axis and the in-plane orientation (Δ ) for the (Y1−xCax)124 powder samples aligned under three different MRF conditions, it was found that MRFs above at least 1 T were required to achieve almost complete tri-axial alignment with Δ < 5°. Irreversibility lines for H c were successfully determined even from the powder samples by the introduction of magnetic alignment without using single crystalline samples. The present study indicates that magnetic alignment is a useful process for the fabrication of quasi-single-crystals from the perspective of solid-state physics and the production of cuprate superconducting materials.