Change in (a) magnetization, M, and (b) electric
polarization, ΔP, vs magnetic field, μ0H. Data were taken in magnetic fields up
to 14 T in a superconducting magnet at sweep rates of 100 Oe/s for
the different temperatures indicated in the legend. Arrows indicate
increasing or decreasing field. Before each scan the temperature was
cooled from above 100 K to the final measurement temperature. The
dashed lines in (a) are calculated Brillouin functions for S = 1, S = 2, and a mixed 1:1 ratio of S = 1 and S = 2 spin states with no orbital
contributions. Upper and lower lines are the lower and upper temperature
limits, respectively (87 and 93 K). Data were collected using millimeter-sized
single crystals of complex 1 mounted with glue to a sapphire
probe with the magnetic field and electric field along the long axis.
Two different crystals were measured in (a) and (b), subject to different
thermal strain conditions which may have caused the difference in
transition temperatures.