In this work, we investigate the effect of interface size on the electrical, magnetoresistive, magnetic and
magnetocaloric properties of the La0.7Ba0.3MnO3 (LBMO) manganite compound. This is done by
introducing different sizes of secondary phases of Ni and Ag (Ni powder, Ni nanowires, Ag oxide powder
and Ag nanoparticles) to the LBMO compound, forming inhomogeneous systems of LBMO/Ni and
LBMO/Ag composites. X-Ray diffraction patterns reveal the interaction lack between Ni & Ag interfaces
and LBMO compound through the coexistence of their characteristic peaks. This suggests the
segregation of these interfaces between LBMO grains, leading to a change in the boundary resistance
that is found to be an interface-size-dependent change. Accordingly, the transport properties of LBMO
are changed, where, the resistivity increases and the metal–semiconductor transition temperature
decreases with the introduced interfaces. The change in grain boundary resistance enhances the
magnetoresistive properties during the promotion of the spin carrier tunnelling process. For instance, the
room temperature low field magnetoresistance of the LBMO compound is enhanced from 1.23% to
4.35, 5.25 and 7.9% with the introduction of Ni powder, Ag nanoparticles and Ag oxide powder
interfaces, respectively. The dc thermal magnetization measurements show a constant value of the
LBMO Curie temperature (Tc) with the introduced interfaces that may be attributed to the complete
interaction lack. However, a small decrease is registered in the Tc value of Ni nanowires doped LBMO
composite, that may be due to the incomplete interaction lack in this composite. Moreover, the
magnetocaloric properties of the LBMO compound show a notable enhancement with the introduced
interfaces, where its relative cooling power is enhanced from 44 J kg1 to 107, 167, 92 and 94 J kg1
with the introduction of Ni powder, Ni nanowires, Ag oxide and Ag nanoparticle interfaces, respectively,
at a 3 T applied magnetic field.