Enhancement magnetic properties of GdMn1−Hf O3 nanoceramics by regulation of vacancy defects and Mn valence state

GdMn _{1− x}Hf _xO ₃ nanoceramics were synthesized by sol–gel method to investigate the regulation of the vacancy defects and Mn valence state on the magnetic properties of GdMn _{1− x}Hf _xO ₃ nanoceramics. XRD and Raman analysis indicated that GdMn _{1− x}Hf _xO ₃ nanoceramics with single-phase structure were synthesized by sol–gel method; Hf ⁴⁺ ions had replaced the Mn ions in GdMnO ₃ and resulted in lattice deformation. SEM measurements verified that all GdMn _{1− x}Hf _xO ₃ nanoceramics had nanoscale particle sizes. XPS analysis indicated that Hf ⁴⁺ substitution could tune the Mn valence state and oxygen vacancy concentration. The results of positron annihilation lifetime spectroscopy revealed that cation vacancies concentration in the interface region could be effectively tailored by Hf ⁴⁺ substitution. The magnetic measurements indicated that appropriate Hf ⁴⁺ substitution could enhance the magnetic transition temperatures and magnetization of GdMnO ₃ samples, which could be mainly attributed to the cation vacancies concentration in the interface region and Mn valence state.