Size modulated Griffiths phase and spin dynamics in double perovskite Sm1.5Ca0.5CoMnO6

Griffiths phase like behavior has been investigated in details in size modulated Sm1.5Ca0.5CoMnO6 double perovskite, having ferromagnetic entities in the paramagnetic matrix. Temperature dependent real and imaginary part of ac susceptibility confirms that Sm1.5Ca0.5CoMnO6-1150 degrees C bulk-sample has spin-glass like ordering below Tg similar to 34.88(3) K. This glassy behavior is attributed to the antisite disorders (similar to 7.12%) along with and magnetic frustration in the system. However, the ground state of Sm1.5Ca0.5CoMnO6-600 degrees C nanometric-sample is observed to be antiferromagnetic in nature due to the presence of large antisite disorder (similar to 53.58%). The observed unusual co-existence of antiferromagnetism with Griffiths-like phase in Sm1.5Ca0.5CoMnO6-600 degrees C sample is rare in nature. Interesting magnetic spin dynamics and aging effect are also observed in both the compounds suggesting different spin relaxation processes in low temperature regime. The observed magnetism in these compounds can be tuned by nearest neighbor Co-O-Mn and/or Co-O-Co/Mn-O-Mn exchange interactions as well as the next nearest neighbor Co-O-O-Co/Mn-O-O-Mn interactions.