100 MHz high-speed strain monitor using fiber Bragg grating and optical filter applied for magnetostriction measurements of cobaltite at magnetic fields beyond 100 T

摘要

High-speed 100 MHz strain monitor using fiber Bragg grating (FBG) and anoptical filter has been devised for the magnetostriction measurements underultrahigh magnetic fields. The longitudinal magnetostriction of LaCoO$_{3}$ hasbeen measured at room temperature, 115, 7 and 4.2 K up to the maximum magneticfield of 150 T. The field-induced lattice elongations are observed, which areattributed to the spin-state crossover from the low-spin ground state toexcited spin-states.