Pressure‐induced electrical resistivity saturation of Fe17Si

Abstract

A large body of work has focused on resistivity saturation in systems where scattering is caused by impurities or by thermal effects. Electrical resistivity saturation is here classified as either static, where impurity scattering causes saturation, or dynamic, where changing external parameters such as temperature or pressure cause saturation. Resistivity measurements up to 5 GPa show pressure-induced resistivity saturation in Fe17wt%Si by the change in sign from positive to negative of the temperature coefficient of resistivity. The pressure dependence of the Curie temperature is 10.2(8) K GPa À1 . The Debye temperature is calculated from the Bloch-Gr€ uneisen equation and yields a pressure dependence of 40 (9) 1 Introduction For many highly disordered metallic systems, specifically d-band alloys near room temperature, experimental observations have shown a negative correlation between the values of electrical resistivity (r) and temperature coefficient of electrical resistivity, TCR [1]. The TCR changes sign from positive to negative in a universal range of 150-200 mV cm. This change in sign of TCR corresponds to saturation of electrical resistivity and can be related to impurity scattering. This behaviour is evident for bulk alloys, thin films and amorphous alloys. Tsuei [2] challenged Mooij's universal range of electrical resistivity saturation and with support of additional experimental observations, he proposed a revised saturation range of 30-400 mV cm. On the other hand, temperature studies on A15 superconductors as well as on transition metal compounds such as iron alloys [3][4][5][6] reported nonlinearity in r(T) and the breakdown of Matthiessen's rule. The growth of r(T) close to room temperature is much faster than expected from Boltzman theory, and at some point it grows much slower than suggested by the Bloch-Gr€ uneisen formula and seems bounded by a value of r max $150 mΩ cm, which was also termed resistivity saturation [4].Seemingly different types of resistivity saturations (impurity induced and temperature induced) described above are suggested to originate from a common source which is based on the Ioffe-Regel criterion [7]. Resistivity

The influence of sulfur on the electrical resistivity of hcp iron: Implications for the core conductivity of Mars and Earth

“…The results show that ρ S is smaller than ρ Si in the pressure range we examined (red line in Figure 2). % and may be invalid at high pressure conditions.Using the present results, we propose the electrical conductivity profiles of the Mars's and Earth's cores containing S. We take the effect of resistivity saturation into consideration in regard to the high P-T resistivity of Fe alloy (ρ tot (T,V)) [Gomi et al, 2013;Kiarasi and Secco, 2015;Ohta et al, 2016;Pozzo and Alfè, 2016]. However, the predicted ρ S from the rule is much smaller than the present ρ S because this empirical rule does not hold high impurity concentration more than 5 at.…”

Electrical Resistivity of Iron Phosphides at High‐Pressure and High‐Temperature Conditions With Implications for Lunar Core's Thermal Conductivity

“…Previous studies indicate that the electrical resistivity of the solid metal and iron alloys (Fe‐Si, Fe‐C) decreases linearly with increasing pressures (Deng et al, ; Ezenwa & Secco, , ; Kiarasi & Secco, ; Silber et al, ; Zhang et al, ). Similar behavior was also observed for iron phosphides in this study (Figure ).…”

“…Dependence of electrical resistivity for Fe‐L compounds with different contents of light elements at room temperature, (a) and (b) are weight and atomic percent, respectively. The resistivity of Fe17Si (17 wt% Si) was measured by Kiarasi and Secco () at the pressures of 2–5 GPa. Colorful solid lines in (b) represent the fit of resistivity data for disordered alloy (Fe‐C, Fe‐P, and Fe‐Si) according to Matthiessen's rule.…”

“…The resistivity for Fe‐P alloy is linear with phosphorus content (P, 0–3.4 at.%) at ambient condition (Węgliński & Kaczmar, ), which agrees with the prediction of Matthiessen's rule. In some scenarios, Matthiessen's rule will break down due to “saturation effect” caused by chemical composition (Gomi et al, ), pressure (Kiarasi & Secco, ), and temperatures (Pozzo & Alfè, ). Also, Wagle et al () observed that the temperature coefficient of resistivity for liquid Fe‐S system changes from positive to negative at high compression and high sulfur concentration.…”

Experimental determination of the electrical resistivity of iron at Earth’s core conditions

“…Matthiessen's rule indicates that element k contributes proportionally to its concentration χ k independently of temperature. Note that this rule does not consider the effect of resistivity saturation, although the measured electrical resistivity of the Fe-Si alloy does show saturation phenomena 40,41 . The high-temperature electrical resistivity, taking the resistivity saturation into account, is well described by a shunt resistor model (see equation (2) and ref.…”