Observation of antiferromagnetic order collapse in the pressurized insulator LaMnPO

Abstract

The emergence of superconductivity in the iron pnictide or cuprate high temperature superconductors usually accompanies the suppression of a long-ranged antiferromagnetic (AFM) order state in a corresponding parent compound by doping or pressurizing. A great deal of effort by doping has been made to find superconductivity in Mn-based compounds, which are thought to bridge the gap between the two families of high temperature superconductors, but the AFM order was not successfully suppressed. Here we report the first observations of the pressure-induced elimination of long-ranged AFM order at ~ 34 GPa and a crossover from an AFM insulating to an AFM metallic state at ~ 20 GPa in LaMnPO single crystals that are iso-structural to the LaFeAsO superconductor by in-situ high pressure resistance and ac susceptibility measurements. These findings are of importance to explore potential superconductivity in Mn-based compounds and to shed new light on the underlying mechanism of high temperature superconductivity.

Electrical resistivity of single crystals of LaFeAsO under applied pressure

“…Studies of this kind have been performed on single crystals of LaMnPO wherein the pressure at which ∆ reaches zero coincides with the emergence of metallic behavior. 32 Our study shows a similar suppression of ∆. The energy gap calculated from data taken in the nearly-hydrostatic cell extrapolates linearly to approximately 6 GPa; unfortunately, this pressure is beyond the limit of the piston cylinder cell.…”

Pressure Induced Superconductivity on the border of Magnetic Order in MnP

“…This is well illustrated by the recent discovery of pressure-induced SC in CrAs [8,9], the first Cr-based unconventional superconductor [10]. This discovery has left manganese (Mn) the only 3d element that does not show SC among any Mn-based compounds, even though a great effort has been devoted recently to explore the possible SC via carrier doping [11] or the application of high pressure [12]. The strong magnetism of Mn is commonly believed to be antagonistic to SC.…”

Robust antiferromagnetism preventing superconductivity in pressurized (Ba0.61K0.39)Mn2Bi2

“…With increasing pressure up to 20.2 GPa, the temperature dependence of real part (χ) of the ac susceptibility remains unchanged. This demonstrates that the T N of the pressurized Ba 0.61 K 0.39 Mn 2 Bi 2 is still higher than 300 K, otherwise it should be detected by our instrument, as done in pressurized LaMnPO9.…”

“…Therefore, the layered AFM compounds with higher Neel temperature ( T N ) are believed to be good candidates for the parent compounds of new high- Tc superconductors6. The Mn-pnicitides of Mn-1111 and Mn-122 compounds, such as LaMnPO789, BaMn 2 P 2 101112, BaMn 2 As 2 13141516171819202122 and BaMn 2 Bi 2 232425, are such kinds of compounds, having AFM ground state similar to the parent compounds of cuprates26 and the same crystal structure as Fe-pnictides23. For such similarities, it is reasonably expected that the BaMn 2 Bi 2 might be a parent compound of Mn-based superconductors.…”