The Structural and magnetic behavior of the Ni_0.5Co_0.5Fe₂O₄ nanocrystalline sample has been studied. The sample has been synthesized by sol–gel auto combustion method. The XRD measurement confirms the single-phase of the Ni_0.5Co_0.5Fe₂O₄ sample. The X-ray diffraction analysis gives the cubic crystal structure with lattice parameter a = 8.3541 Å. The FESEM measurement shows homogeneity in the sample and the EDAX measurements clearly indicates that the elements in the sample are appropriate. The magnetization measurements were measured in different modes i.e., ZFC and FC in the temperature range of 2 K − 300 K under the presence of 50 Oe. The M−T measurements show the irreversibility in the ZFC and FC measurements which suggest the magnetic relaxation in the sample. The M−H loops were performed at 5 K and 300 K temperatures by using variable fields upto ± 5 T. It suggests that the retentivity, coercivity, and saturation magnetization of the sample make it a potential candidate for medical diagnosis applications.