Spin and orbital moments in ${\text{Fe}}_3{\text{O}}_4$

We report a study of the spin moment in ${\text{Fe}}_3{\text{O}}_4$ as a function of temperature using spin-dependent Compton scattering. Magnetic Compton profiles and spin moment values were obtained either side of the Verwey transition for applied magnetic fields of 2.5 and 7 T. The orbital moments, determined by comparison with bulk magnetometry, are almost fully quenched. No evidence of any anomalies in the spin or orbital moments at the Verwey transition was observed. The magnetic Compton profiles have the characteristic shape for $\text{Fe}3d$ electrons at all temperatures with no changes in the degree of anisotropy across the Verwey transition. Our data are consistent with the highly spin-polarized electronic structure expected for bulk ${\text{Fe}}_3{\text{O}}_4$.

Figure 1

(Color online) (a) The experimental MCPs at a temperature of $T=100\text{K}$, for a magnetic field of 2.5 T applied along the [100], [110], and [111] crystallographic directions in ${\text{Fe}}_3{\text{O}}_4$, represented by open red circles, solid blue triangles, and solid green circles, respectively. The inset shows the low momentum region in more detail. (b) Profiles at $T=100\text{K}$ (blue circles) and $T=300\text{K}$ (red triangles) for the three directions. The statistical error is smaller than the size of the symbols.

Figure 2

(Color online) The experimental spin moment observed with a magnetic field of 2.5 T applied along the [100], [110], and [111] crystallographic directions in ${\text{Fe}}_3{\text{O}}_4$. The directions are indicated by red circles, blue triangles, and green circles, respectively. The Li et al. (Ref. 20) data, measured in a 7 T magnetic field, for the [110] direction are shown as filled triangles.

Figure 3

(Color online) Spin moment in ${\text{Fe}}_3{\text{O}}_4$ for a magnetic field of 7 T applied along the [110] crystallographic direction (open circles), together with the Li et al. (Ref. 20) data as filled triangles. Also shown is the total magnetization at 7 T as measured in a SQUID (black). The error bars shown for the magnetization indicate the overall systematic error rather than a point-to-point statistical error.