Temperature Dependence of Exchange Coupling on Magnetic funnel Junctions

Magnetic funnel Junctions (MTJs) were fabricated on thermally oxidized Si (100) wafers using DC magnetron sputtering. The film Structures were Ta(50 ${\AA}$)/CU(100 ${\AA}$)$Ni_{80}Fe_{20}(20 $ ${\AA}$)/Cu(50 ${\AA}$)/$Mn_{75}Ir_{25}(100 $ ${\AA}$)/$Co_{70}Fe_{30}(25$ ${\AA}$)/Al-O(15 ${\AA}$)/$Co_{70}Fe_{30}(25 $ ${\AA}$)/$Ni_{80}Fe_{20}(t)/Ta(50 $ ${\AA}$), with t=0 ${\AA}$, 100 and 1000 ${\AA}$, respectively. X-ray diffraction has shown improvement of (111) texture of IrMn$_3$ and Cu by annealing. The exchange-biased energy is almost inversely proportional to temperature. The difference between the coercivity H$_c$ and the exchange biased field H$_E$ for t = 0 $_3$ sample is smaller than that for t = 1000 ${\AA}$. For the pinned layer, the decreasing rate of the coercivity with the temperature is higher compared to that of the exchange field, but variation of H$_c$ is similar to that of the exchange field for free layer.