Magnetic-field enhancement of nonlocal spin signal in Ni${}_{80}$Fe${}_{20}$/Ag lateral spin valves

We observe a magnetic-field-induced enhancement of the nonlocal spin signal in Ni${}_{80}$Fe${}_{20}$/Ag lateral spin valves. The enhancement depends on the bias current polarity but not on the field direction. We present a theoretical model that explains our experimental results, taking into account the electron-spin relaxation of magnetic impurities. We find that the relaxation is about an order of magnitude weaker than Elliott-Yafet relaxation.

Figure 1

(a) A scanning electron microscopy image of a Py/Ag LSV device adapted to show the nonlocal measurement configuration for a positive bias current polarity. (b) $R_{NL}$ vs $B_{\parallel }$ at 4.4 K and the corresponding $\Delta R_s$ signal. (c) $R_{NL}$ vs $B_{\perp }$ measured on the same sample at 4.5 K. $\delta R_{NL}$ at $B\sim 2$ T is marked by an arrow.

Figure 2

(a) Magnetic-field dependence of $R_{NL}$ measured at 40 K for $B_{\perp }$ (solid circles) and $B_{\parallel }$ (open circles) to the initial magnetization orientation of Py electrodes.

Figure 3

(a)–(d) $\delta R_{NL}$ vs $B_{\parallel }$ for positive (solid circles) and negative (open circles) polarity of the LSV bias current. The fits to the data based on Eq. (4) are shown as solid red (positive bias) and dashed blue (negative bias) lines. The measurement temperatures are indicated in the graphs.

Figure 4

$T$ dependencies of (a) parameter $a$ and (b) parameter $\beta$ extracted from fitting $\delta R_{NL}\left(B\right)$ using Eq. (4). The value of ${\alpha }_R=4$ was assumed in fitting.