Spin-flop transition in samarium metal investigated by capacitance dilatometry in a steady magnetic field of $45\mathrm{T}$

The longitudinal and transversal forced magnetostrictions of a single crystal of samarium metal have been investigated in a static magnetic field up to $45\mathrm{T}$. The data show pronounced features of a spin-flop transition initiating at an applied field of about $30\mathrm{T}$. The measured forced magnetostriction is about 1 order of magnitude smaller than the spontaneous magnetostriction. Based on a model calculation of the magnetic phase diagram these features have been interpreted within the exchange striction model. The moments of the quasicubic Sm sites enter a spin-flop phase at about $30\mathrm{T}$ and ferromagnetic saturation is predicted at $60\mathrm{T}$. Similarly the model predicts a spin-flop phase for the hexagonal Sm sites at $140\mathrm{T}$ and ferromagnetic saturation at $390\mathrm{T}$.

Figure 1

Forced magnetostriction data of a Sm single crystal (symbols). The longitudinal and transverse components are shown. The data at lower fields were taken from Rotter et al. (Ref. 11). The basal components show a negative effect at a field of about $33\mathrm{T}$. The $c$ axis expands at the same magnetic field. In the lower part of the figure the volume effect of the magnetostriction is shown. Compared to the striction along the three axes, the volume change is small at the spin-flop transition. Lines denote results of the model calculation described in the text.

Figure 2

Temperature dependence of the transversal magnetostriction and parastriction ${ϵ}^a$ for magnetic field along the $c$ axis. For comparison, the thermal expansion data ${ϵ}^a$ in zero field are shown in the inset.

Figure 3

Temperature dependence of the transversal magnetostriction ${ϵ}^b$ for magnetic field along the $c$ axis.

Figure 4

Thermal expansion of a Sm single crystal in zero magnetic field. Symbols indicate experimental data (taken from Ref. 11), dashes the fit of a Debye model to the paramagnetic range (phonon contribution to the thermal expansion), and dots the results of the exchange striction model described in the text.

Figure 5

Experimental data of susceptibility (Ref. 15) (symbols) in comparison with results of the model calculation (solid lines) described in the text.

Figure 6

Experimental data of magnetization (Ref. 15) (symbols) and results of the model calculation (solid lines) described in the text.

Figure 7

Calculated magnetic phase diagram of Sm with magnetic field applied along the $c$ axis (for details see text). The description denotes $\mathrm{CC}=\text{cubic}$ collinear, $\mathrm{CSF}=\text{cubic}$ spin flop, $\mathrm{HC}=\text{hexagonal}$ collinear, and $\mathrm{HSF}=\text{hexagonal}$ spin flop. The open circles show results from high field magnetostriction measurements.