  Temperature dependent magnetization study on single phase orthorhombic
Ruddlesden-Popper manganite Ca3Mn2O7 evidences antiferromagnetic (AFM) ordering
below 123K. Field-dependent magnetization M(H) depicts off-centered hysteretic
loops below ~110K-- confirming the existence of both weak ferromagnetism (WFM)
and exchange bias, whose development upon cooling is examined in detail. WFM is
attributed to the formation of uncompensated-spin-clusters within the
AFM-matrix, stabilized by the high-anisotropy in the manganite, favoring
Dzyaloshinskii-Moriya (D-M) interaction. Temperature dependence of an evaluated
average canting angle from the M(H) loops provides a quantitative measure of
the WFM-evolution. Dielectric measurements exhibit magneto-conductive effects
concurrent to the WFM-onset. Temperature dependence of the
low-frequency/dc-limit of Jonscher-fits to the conductivity isotherms confirms
the presence of relatively more-conductive clusters, embedded in the
insulating-bulk. Nyquist impedance-analysis of complex impedance reveals two
relaxations, yielding dual magnetic-field effects; the lumped circuit
parameters feature anomalies across the magnetic phase changes.

Materials Science