Abstract
We report a pronounced peak effect in the magnetization of single crystals with critical temperatures ranging between 7.1 and 5.0 K, and single crystals with critical temperatures down to 3.4 K. We correlate the peak effect in magnetization with the structure of the vortex lattice across the peak-effect region using scanning-tunneling microscopy. Magnetization measurements show that the amplitude of the peak effect in the case of exhibits a nonmonotonic behavior as a function of the Co content, reaching a maximum for concentration of Co of about (corresponding to a of 5.7 K) and after that gradually decreasing in amplitude with the increase in the Co content. The normalized value of the peak position has weak dependence on Co concentration. In the case of the features of the peak effect as a function of the Mn content are different and they can be understood in terms of strong pinning.
- Received 1 August 2008
DOI:https://doi.org/10.1103/PhysRevB.78.174518
©2008 American Physical Society