Visualizing ferroic domains in an all-in–all-out antiferromagnet thin film

Antiferromagnetic domain distribution is analyzed by a scanning superconducting quantum interference device microscopy for a pyrochlore $\mathrm{T}{\mathrm{b}}_2\mathrm{I}{\mathrm{r}}_2{\mathrm{O}}_7$ thin film with an all-in–all-out (AIAO) spin arrangement. The local magnetic field on the surface is found to originate predominantly from the $\mathrm{T}{\mathrm{b}}^{3+}(J=6)$ magnetic moment. While $\mathrm{I}{\mathrm{r}}^{4+}$ magnetic moment ($J_{\mathrm{eff}}=1/2$) is too small to detect even below the Néel temperature (120 K), $\mathrm{T}{\mathrm{b}}^{3+}$ AIAO domains grow below 40 K following the background $\mathrm{I}{\mathrm{r}}^{4+}$ domains rather than the external magnetic field, clarifying the decisive role of Ir-Tb exchange interaction in magnetic ordering.

Figure 1

(a) Schematics of (top) Tb and Ir sublattices of $\mathrm{T}{\mathrm{b}}_2\mathrm{I}{\mathrm{r}}_2{\mathrm{O}}_7$ and (bottom) all-in–all-out antiferromagnetic ordering of a $\mathrm{T}{\mathrm{b}}^{3+}$ tetrahedron. (b) Schematic of scanning SQUID measurement for a $\mathrm{T}{\mathrm{b}}_2\mathrm{I}{\mathrm{r}}_2{\mathrm{O}}_7$ thin film grown on a YSZ (111) substrate. The diameter of the pick-up loop is 10 μm. Temperature dependence of (c) resisitivity and (d) magnetization of the $\mathrm{T}{\mathrm{b}}_2\mathrm{I}{\mathrm{r}}_2{\mathrm{O}}_7$ thin film. The magnetization is measured after ZFC and FC with $\pm 0.2\mathrm{T}$ with increasing temperature under a field strength of $+0.2\mathrm{T}$ applied along [111]. (e) Magnetic-field dependence of resistivity at 2 K.

Figure 2

(a)–(f) Scanning SQUID images at different temperatures after ZFC. The size of the images is $60\mu \mathrm{m}\times 60\mu \mathrm{m}$. (g) Temperature dependence of the root-mean-square of magnetic field for the scanning SQUID images. The scaled neutron intensity from $\mathrm{T}{\mathrm{b}}^{3+}$ magnetic moment is also shown for comparison, which is taken from Ref. [13].

Figure 3

Scanning SQUID images of (a) ZFC, (b) FC $(-0.1\mathrm{T})$ from 50 K, and (c) FC ($+0.1\mathrm{T}$) from 130 K. A negative magnetic field is applied when field cooling for (b), while it is positive for (c). The measurement temperature is 4.7 K for all the data. The magnetic field is applied in the cooling processes with a NdFeB permanent magnet placed just above the sample.

Figure 4

(a) Magnetoresistance at 2 K after the sample is cooled from 130 K under $\pm 0.2\mathrm{T}$. The α value is defined as linear component of magnetoresistance per magnetic field. (b) The α value as a function of cooling magnetic field.