RESUMO
CaBaCo4O7 (CBCO) cobaltite shows a giant spin driven pyroelectric polarization below its ferrimagnetic transition temperature at 64 K. In the present study, we have investigated the structural, magnetic and electric polarization properties of light nonmagnetic Zn doped polycrystalline CaBaCo3.97Zn0.03O7 (CBCZO) cobaltite. Neutron powder diffraction studies on the CBCZO show that the Zn occupies the Co2 sites which lowers the strength of the magnetic interactions between the bitetrahedral cobalt c-axis chains. Further, we show that these chains act as magnetic clusters and causes the switching of the electric polarization. This study specifies that the ferrimagnetic-pyroelectric ground state of CBCO is very sensitive to the light non-magnetic doping and the results can be used to further understand the pyroelectric polarization switching properties of CBCO.
RESUMO
The magnetic glassy state is a fascinating phenomenon, which results from the kinetic arrest of the first order magnetic phase transition. Interesting properties, such as metastable magnetization and nonequilibrium magnetic phases, are naturally developed in the magnetic glassy state. Here, we report magnetic glass property in the low spin state of Co3+ in EuBaCo2O5+δ (δ = 0.47) cobaltite at low temperature (T < 60 K). The measurements of magnetization under the cooling and heating in unequal fields, magnetization relaxation and thermal cycling of magnetization show the kinetic arrest of low magnetization state below 60 K. The kinetically arrested low temperature magnetic phase is further supported through the study of isothermal magnetic entropy, which shows the significant entropy change. The present results will open a new window to search the microscopic relation between the spin state transitions and the kinetic arrest induced magnetic glassy phenomena in complex materials.