a second magnetic metal layer which is provided between the second magnetic material layer and the second surface of the first nonmagnetic layer, and which includes at least one element selected from Fe, Co and {HEAD ~ Ni}, the second magnetic metal layer being {TAIL ~ exchange} coupled to the second magnetic material layer, and having a damping constant smaller than that of the second magnetic material layer, 
a second magnetic metal layer which is provided between the second magnetic material layer and the second surface of the first nonmagnetic layer , and which includes at least one element selected from Fe , Co and { HEAD ~ Ni } , the second magnetic metal layer being { TAIL ~ exchange } coupled to the second magnetic material layer , and having a damping constant smaller than that of the second magnetic material layer ,
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