Figure 1

A part of the ${}^{11}\mathrm{B}\mathrm{\text{−}}\mathrm{NMR}$ spectra covering the most negative range of internal field obtained at $T=0.43\mathrm{K}$ in various magnetic fields. The values of magnetic fields correspond to the position of the spectral base line on the vertical axis. The purple (below $28.2\mathrm{T}$), red ($28.7–29.2\mathrm{T}$), blue ($31.5–32.2\mathrm{T}$), and green (above $33.6\mathrm{T}$) spectra belong to the $1/8$, $2/15$, $1/6$, and $1/4$ plateaus, respectively.Reuse & Permissions

Figure 2

Inset: The magnetic-field dependence of the torque divided by field at $T=60\mathrm{mK}$ for the sample positioned at $\pm 10\mathrm{mm}$ off the nominal field center. Main panel: The thick black line represents the longitudinal magnetization (see the text) with the vertical scale appropriately adjusted. The magnetization values at $1/8$, $2/15$, $1/6$, and $1/4$ of the saturation are shown by the dashed lines. The horizontal bars indicate the field range of the plateaus determined by NMR. The open circles show the magnetization determined from the Cu-NMR shift data from Ref. 8.Reuse & Permissions

Figure 3

(a) Deconvoluted ${}^{11}\mathrm{B}\mathrm{\text{−}}\mathrm{NMR}$ spectra representing the distribution of $H_{\mathrm{int}}$ obtained at $T=430\mathrm{mK}$ unless explicitly indicated. The data for the $1/8$ plateau at 27.5 T were taken from Ref. 9. (b) An extended triplet and the nearest neighbor $\mathrm{B}$ sites. (c) The crystal structure of ${\mathrm{SrCu}}_2({\mathrm{BO}}_3{)}_2$. The arrows indicate the hyperfine coupling of a $\mathrm{B}$ site to the nearest and the second nearest Cu on the same layer (A1 and A2) as well as the coupling to the third and fourth neighbors on the adjacent layers (A3 and A4). (d) The spin superstructure for the plateau phases. The thin black lines show the lattice of orthogonal Cu dimers in one layer. The thick red (dark) lines show the triplet dimers carrying the largest magnetization $m_0$ in the same layer while the blue (pale) lines indicate these triplets on the neighboring layers. The unit cell of each superstructure is shown by the shaded area.Reuse & Permissions

Figure 4

Distribution of local magnetization in the $1/8$, $1/6$, $1/4$, and $1/3$ plateau phases deduced from the peak positions of the B-NMR spectra.Reuse & Permissions