A propagating Majorana mode: Although Majorana fermions remain elusive as elementary particles, their solid-state analogs have been observed in hybrid semiconductor-superconductor nanowires. In a nanowire setting, the Majorana states are localized at the ends of the wire. He et al. built a two-dimensional heterostructure in which a one-dimensional Majorana mode is predicted to run along the sample edge (see the Perspective by Pribiag). The heterostructure consisted of a quantum anomalous Hall insulator (QAHI) bar contacted by a superconductor. The authors used an external magnetic field as a “knob” to tune into a regime where a Majorana mode was propagating along the edge of the QAHI bar covered by the superconductor. A signature of this propagation—half-quantized conductance—was then observed in transport experiments. Science , this issue p. 294 ; see also p. 252

Single-crystal bismuth thin films 1 to 20 micrometers thick were fabricated by electrodeposition and suitable annealing. Magnetoresistance up to 250 percent at 300 kelvin and 380,000 percent at 5 kelvin as well as clean Shubnikov–de Haas oscillations were observed, indicative of the high quality of these films. A hybrid structure was also made that showed a large magnetoresistive effect of 30 percent at 200 oersted and a field sensitivity of 0.2 percent magnetoresistance per oersted at room temperature.

We investigate the magnetization reversal in ${[\mathrm{Co}\left(4\mathrm{\AA }\right)∕\mathrm{Pt}\left(7\mathrm{\AA }\right)]}_{50}$ multilayers with perpendicular magnetic anisotropy both macroscopically by the first-order reversal curve (FORC) technique and microscopically by transmission x-ray microscopy (TXRM) and resonant x-ray small angle scattering (SAS). In particular, we focus on the nucleation and saturation processes. The onset of magnetization reversal is dominated by irreversible processes corresponding to the avalanchelike propagation of one-dimensional stripe domains that originate from earlier nucleated zero-dimensional bubble domains. In a second stage we observe mainly reversible behavior where the overall domain topology is preserved. Finally another irreversible process brings the sample to negative saturation, corresponding to the contraction and annihilation of domains. Interestingly, even well beyond the apparent major-loop saturation field, the FORC diagram exhibits pronounced irreversible switching and thus provides a direct measure of the true (and significantly higher) saturation field. TXRM and SAS measurements reveal on a microscopic level that some residual bubble domains with negligible moments still persist for fields well above the apparent saturation field. These residual domains, if unannihilated, significantly alter the subsequent magnetization reversal.