In-plane and interlayer magnetoresistance in FeSe

Abstract

We report measurements of the in-plane and interlayer magnetoresistances of FeSe. The in-plane magnetoresistance $Δρ_{ab}/ρ_{ab}(0)$ for $B \parallel c$ is positive below $T_s$ and increases with decreasing temperature, exceeding 2.5 at $T$ = 10 K and $B$ = 14 T. The field-direction dependence indicates that the in-plane magnetoresistance is basically determined by the $c$-axis component of the magnetic field. The interlayer magnetoresistance $Δρ_{c}/ρ_{c}(0)$ is negative below $T_s$ but turns positive below $\sim$18 K, which is probably due to the contamination by the large in-plane magnetoresistance. The field-direction dependence of the interlayer magnetoresistance can approximately be described by a standard formula for quasi-two-dimensional electron systems except near $B \parallel ab$. The experimental magnetoresistance near $B \parallel ab$ is larger than the formula, which can be attributed to the so-called interlayer coherence peak. The large width of the peak indicates the correspondingly large interlayer transfer energy.

Figures (7)

• Figure 1: (Color online) Temperature dependence of in-plane resistivity $\rho_{ab}$ in FeSe sample 1 ($0.64 \times 0.8 \times 0.02$ mm$^3$). The data for $B$ = 0 and $B$ = 14 T applied parallel to the $ab$ plane and along the $c$ axis are shown. The left inset shows the geometry of the current $I$ and the magnetic field $B$ schematically. The in-plane field is approximately at a 50$^{\circ}$ angle from the current. The right inset shows the in-plane magnetoresistance $\Delta \rho_{ab} / \rho_{ab}(0)$ at $B$ = 14 T for $B \parallel ab$ and $B \parallel c$.
• Figure 1: (Color online) In-plane magnetoresistance in FeSe sample 2 as a function of $B\cos\theta$. The data in Figs. 2(a) and 2(b) are plotted as a function of $B\cos\theta$, the $c$-axis component of the applied field.
• Figure 1: (Color online) Interlayer resistivity contaminated by in-plane resistivity in FeSe sample 3 ($0.75 \times 0.68 \times 0.08$ mm$^3$). (a) 'Interlayer resistivity' versus temperature at $B$ = 0 and 14 T applied parallel to the $c$ axis. The inset shows the corresponding magnetoresistance. (b) Magnetoresistance at $T$ = 10 K as a function of the magnetic field parallel to $c$. A fit to $\alpha B^n$ (broken line) gives $\alpha$ = 0.03052(4) and $n$ = 1.2478(5). (c) Magnetoresistance at $T$ = 20 K and $B$ = 14 T as a function of the field angle $\theta$. Three field rotation planes $\phi$ = 0, 45, and 90$^{\circ}$ were used. A fit to $\alpha (\cos B)^n + c$ (broken line) gives $\alpha$ = 0.470(1), $n$ = 1.335(7), and $c$ = 0.036(1).
• Figure 2: (Color online) Magnetoresistance effects on in-plane resistivity in FeSe sample 1. (a) In-plane magnetoresistance $\Delta \rho_{ab} / \rho_{ab}(0)$ as a function of magnetic field along the $c$ axis measured at $T$ = 30 K. A fit to $\alpha B^n$ (broken line) gives $\alpha$ = 0.01433(2) and $n$ = 1.512(1). (b) In-plane magnetoresistance at $T$ = 30 K and $B$ = 14 T as a function of $\theta$, which is the polar angle of the magnetic field direction measured from the $c$ axis. The azimuth angle $\phi$ specifies the rotation plane of the magnetic field and was varied from $\phi$ = 90 to -75$^{\circ}$ in steps of 15$^{\circ}$. The broken line shows $\alpha (B \cos \theta) ^n$ with the same values of $\alpha$ and $n$ as in (a). The inset explains the field angles $\theta$ and $\phi$. The origin of $\phi$ is defined with respect to the sample holder, not to a crystal axis.
• Figure 2: (Color online) Interlayer resistivity contaminated by in-plane resistivity in FeSe sample 4 ($1.1 \times 0.64 \times 0.24$ mm$^3$). (a) 'Interlayer resistivity' versus temperature at $B$ = 0. (b) Magnetoresistance at $T$ = 8 K and $B$ = 14 T as a function of the field angle $\theta$. Three field rotation planes $\phi$ = -45, 0, 45, and 90$^{\circ}$ were used.