Spin valve element driving method and spin valve element

A spin valve element driving method for obtaining an electromagnetic signal from a spin valve element, the spin valve element including an intermediate layer, which is an insulating layer or an electrically conductive nonmagnetic layer, and a pair of ferromagnetic layers including a fixed layer and a free layer sandwiching the intermediate layer, the fixed layer having a higher coercivity than the free layer, and being magnetized in a direction substantially perpendicular to a film plane thereof,

• the method comprising a driving step of passing current from one of the pair of ferromagnetic layers to the other through the intermediate layer, wherein
• in the driving step, an amount X of the current and the value Y of a magnitude of an external magnetic field satisfy both
• a first condition:
• (A+BYD)2−4AD(BY−CX)>0
• and
• a second condition:
• −1<((A+BYD)−((A+BYD)2−4AD(BY−CX))0.5)/(2AD)<((A+BYD)+((A+BYD)2−4AD(BY−CX))0.5)/(2AD)<1
• when A>0;
• and
• ((A+BYD)−((A+BYD)2−4AD(BY−CX))0.5)/(2AD)<1
• when A<0, where
• X is positive when the current passes from the free layer toward the fixed layer,
• A=αγHu and B=αγ, α being the Gilbert damping constant, γ being the gyromagnetic ratio, and Hu being the component of the magnetic field, which is the sum of a magnetocrystalline anisotropy field crystal anisotropy magnetic field and a demagnetizing field of the free layer, perpendicular to the free layer, and
• C=μP/(Ms×V×e) and D=P2 if the intermediate layer is an insulating layer, and C=(μP/(Ms×V×e))/(−16+3(P1/2+P−1/2)3) and D=(P1/2+P−1/2)3/(−16+3(P1/2+P−1/2)3) if the intermediate layer is an electrically conductive nonmagnetic layer, P being a spin polarization, μ being a Bohr magneton, Ms being a saturation magnetization of the free layer, V being a volume of the free layer, and e being an electronic charge.