We have studied the effects of a magnetic field on the magnetism and transport
properties of the layered manganites
R1/2Sr3/2MnO4
(R = La and Nd) in pulsed magnetic fields up to
40 T. The R = La crystal shows metamagnetic-like
transitions above 30 T, concomitantly with a colossal magnetoresistance (CMR)
effect as large as [ρ(0) - ρ(H)]/ρ(H) >
103 with a field of µοH = 38 T at low
temperatures. These transitions can be ascribed to the field-induced melting
of the real-space ordering of the
eg electrons (charge ordering).
For the R = Nd crystal, a magnetic field along
the c-axis enhances the two-dimensionality in the
conductivity. Moreover, we observed metamagnetic-like transitions accompanied
by the CMR effects at low temperatures, in spite of the absence of charge
ordering.
A Method of Critical Magnetic‐Field Measurement for High‐Field Superconductors in Pulsed Magnetic Fields
