Top spin valve films with PtMn antiferromagnetic layers were deposited using a multi-target dc magnetron sputtering in (100)Si substrates overcoated with 500 $AA$ of Al$_2$O$_3$. Firstly, the post-deposition annealing was performed at 270$^{C}$ in a unidirectional magnetic field of 3 kOe to induce the crystallographic transformation of the PtMn layer from a fcc (111) to a fct (111) structure. Secondly, the spin valve films were annealed without magnetic fields and magnetic properties were measured. In Si/A1$_2$O$_3$ (500$AA$)/Ta(50$AA$)NiFe(40$AA$)/CoFe(17$AA$)/Cu(28$AA$)/CoFe (30$AA$)PtMn(200$AA$)Ta(50$AA$) top spin valve samples, the MR ratio decreased slowly with increasing annealing temperature up to 325$^{C}$. But above 325$^{C}$, the MR ratio decreased rapidly to 1%, due to a collapse of the exchange coupling between a antiferromagnetic layer and a pinned layer with increasing annealing temperature. Also above 325$^{C}$, the exchange biased field rapidly decreased and the interlayer coupling field rapidly increased with increasing annealing temperature. A change in the interlayer coupling field was resulted from the increase in interface roughness due to Mn-interdiffusion through the grain boundaries. We confirmed the temperature in changing magnetic properties agreed well with the blocking temperature of PtMn based spin valve structure.