Observation of lock-in phenomena in heavy-ion-irradiated single crystal of $\mathrm{Ba}({\mathrm{Fe}}_{0.93}$Co${}_{0.07}$)${}_{2}$As${}_{2}$

Observation of lock-in phenomena in heavy-ion-irradiated single crystal of $Ba ({Fe}_{0.93}$ Co $_{0.07}$ ) $_{2}$ As $_{2}$

Toshihiro Taen, Hidenori Yagyuda, Yasuyuki Nakajima, Tsuyoshi Tamegai, Oscar Ayala-Valenzuela, Leonardo Civale, Boris Maiorov, Tadashi Kambara, and Yasuyuki Kanai

Phys. Rev. B 89, 024508 – Published 22 January 2014

Abstract

The angular dependence of magnetization was measured in an optimally Co-doped BaFe $_{2}$ As $_{2}$ single crystal, which is irradiated by 2.6 GeV uranium to introduce columnar defects (CDs). At low fields ( $H$ ), we observe the irreversible magnetization $M_{irr}$ insensitive to the angle $θ$ around $H ∥ CDs$ . The field dependence of the angular range $2 θ_{L}$ is proportional to $1 / H$ , quite consistent with the expectation of the lock-in transition. This manifests the first observation of the fingerprint of the Bose glass phase in iron-based superconductors.