Growth, Annealing Effects on Superconducting and Magnetic Properties and Anisotropy of FeSe_1-x_Te_x_ (0.5 =< x =< 1) Single Crystals

TL;DR

This study investigates how growth and annealing affect the superconducting and magnetic properties, including anisotropy, of FeSe_1-x_Te_x_ single crystals with x between 0.5 and 1.

Contribution

It provides new insights into the effects of annealing on superconductivity and anisotropic properties of FeSe_1-x_Te_x_ crystals, especially for x=0.6.

Findings

Annealing induces bulk superconductivity in FeSe_1-x_Te_x_ crystals.

The resistivity shows metallic behavior in-plane and a broad maximum out-of-plane.

The anisotropic parameter gamma is approximately 2.7 near T_c.

Abstract

Single crystals of FeSe_1-x_Te_x_ (0.5=<x=<1) have been grown by the Bridgman method. After annealing them at 400 deg for 100 h in vacuum, single crystals of x=0.5-0.9 have exhibited bulk superconductivity. Anisotropic properties of the electrical resistivity and upper critical field, H_c2_, have been investigated for the single-crystal FeSe_1-x_Te_x_ with x=0.6. It has been found that the in-plane resistivity, Rho_ab_, shows a metallic temperature-dependence, while the out-of-plane resistivity, Rho_c_, shows a broad maximum around 100 K. The resistivity ratio, Rho_ab_/Rho_c_, is 44 and 70 at 290 K and just above the superconducting transition temperature, T_c_, respectively. The anisotropic parameter, gamma= H_c2_^para^/H_c2_^perp^ (The para and perp indicate field directions parallel and perpendicular to the ab-plane, respectively.), is estimated as 2.7 just below T_c_.