Determination of melting curves of metals from resistance changes in the LHDAC

A new method for determining melting temperatures of metals at high pressure is presented. The resistivity of laser-heated wires shows strong, discontinuous behavior both for solid-solid transitions and melting. In this technique we have used the split gasket method$^{\mathrm{1}}$, where the two gasket halves act as electrical leads for metal wires with dimensions 10 x 25 micron. Both alumina powder and KCl were used as pressure media. The wires were heated with an ytterbium fiber laser ($\lambda \quad =$ 1070 nm, TEM$_{\mathrm{00}}$ mode, CW, IPG-Photonics). Changes in the electrical resistance of the sample wire were measured by the two-terminal method using source meter (Keithley 2400) under a constant direct current of 100~mA. Iron was chosen as the test case for this new technique. Melting data up to 1 Mbar and 3200 K are reported showing a significant deviation from recently reported X-ray measurements$^{\mathrm{2}}$. Our new measurement for iron show melting temperature of iron consistent with previous findings of Boehler (1993)$^{\mathrm{3}}$ and Aquilanti \textit{et al}. (2015)$^{\mathrm{4}}$. References: 1) R. Boehler, Geophys. Res. Lett. \textbf{13}, 1153 (1986). 2) S. Anzellini \textit{et al.}, Science \textbf{340}, 464 (2013). 3) R. Boehler, Nature \textbf{363}, 534 (1993). 4) G. Aquilanti, PNAS \textbf{112}, 12042 (2015).