α−β and β−γ phase boundaries of solid oxygen observed by adiabatic magnetocaloric effect

Abstract

The magnetic-field-temperature phase diagram of solid oxygen is investigated by the adiabatic magnetocaloric effect (MCE) measurement with pulsed magnetic fields. Relatively large temperature decrease with hysteresis is observed at just below the β-γ and α-β phase transition temperatures owing to the field-induced transitions. The magnetic field dependences of these phase boundaries are obtained as T βγ (H) = 43.8 − 1.55 × 10 −3 H 2 K and T αβ (H) = 23.9 − 0.73 × 10 −3 H 2 K. The magnetic Clausius-Clapeyron equation quantitatively explains the H dependence of T βγ , meanwhile, does not T αβ . The MCE curve at T βγ is of typical first-order, while the curve at T αβ seems to have both characteristics of first-and second-order transitions. We discuss the order of the α-β phase transition and propose possible reasons for the unusual behavior.

Physical properties of liquid oxygen under ultrahigh magnetic fields

“…The reversible results indicate that any temperature change (e.g., magnetocaloric effect) is negligible in this experimental setup (see also Ref. [47]). At 90 T, v decreases by 8.5 % without any sign of saturation.…”

“…For a paramagnet, the magnetic entropy rapidly changes near the saturation field of magnetization. Therefore, the temperature change could be much larger than the reported value (∼ +1 K at 50 T) [47]. At increased temperatures, the anomaly related to the LLT might become too weak.…”

“…9(d), the calculated absorption intensity is plotted using the parameters J/k B = −15 K and T = 79 K. The experimental results are larger than the calculated value, but the difference at the top of the field is within the experimental error. The difference might come from the pressure increase due to the magnetovolume effect or magnetocaloric effect [47].…”

Precursor of a magnetic-field-induced liquid-liquid transition of oxygen

“…The reversible results indicate that any temperature change (e.g., due to a magnetocaloric effect) is negligible in this experimental setup (see also Ref. [36]). At 90 T, v decreases by 8.5 % without any sign of saturation.…”

“…In the whole temperature range, a monotonic decrease of v is observed without any hysteresis. The reversible results indicate that any temperature change (e.g., due to a magnetocaloric effect) is negligible in this experimental setup (see also Ref [36]…”