Stern-Gerlach Experiments on $\mathrm{Mn}@{\mathrm{Sn}}_{12}$: Identification of a Paramagnetic Superatom and Vibrationally Induced Spin Orientation

Beam deflection experiments in inhomogeneous magnetic fields reveal a new limiting case of the magnetization distribution of isolated clusters. Endohedrally doped clusters are produced in a temperature controlled, cryogenically cooled laser ablation source. Temperature dependent experiments indicate a crucial contribution of molecular vibrations to the spin dynamics of $\mathrm{Mn}@{\mathrm{Sn}}_{12}$. In its vibrational ground state the cluster behaves magnetically like a paramagnetic atom, with quantized spin states. However, excited molecular vibrations induce spin orientation in the magnetic field.

Figure 1

Beam profiles of $\mathrm{Mn}@{\mathrm{Sn}}_{12}$ at $T_{\mathrm{nozzle}}=16\mathrm{K}$ without (dots) and with (squares) a magnetic field applied. The simulated BP at 1.6 T (red line) is the sum of six individual beam components of equal magnitude (dashed black lines) shifted by an amount proportional to the quantized $z$ component of the electronic spin angular momentum $S_z\hslash$, at velocity $v$ of the cluster.

Figure 2

Beam profile of $\mathrm{Mn}@{\mathrm{Sn}}_{12}$ at $T_{\mathrm{nozzle}}=30\mathrm{K}$ (a), 50 K (b), and 70 K (c) without (dots) and with (squares) a magnetic field applied. The simulated BP at 1.6 T (red line) is obtained as the sum of a contribution from the superatomic model (dotted line, $P_0$) and a contribution showing Brillouin-like response (dashed line, $P_1$). The contribution $P_0$ is given by the product of individual ground state populations of Jahn-Teller active modes $P_{0,i}(T_{\mathrm{nozzle}})$ (see Table ) and $P_1=1-P_0$. The range of slit positions is adjusted to the decreasing effect of the magnetic field at higher velocities $v$.