Transition metal-pnictide systems have been extensively studied for decades owing to their unique magnetic properties. Among these, chromium arsenide (CrAs) and manganese phosphide (MnP) are the first chromium and manganese based superconductors, exhibiting unconventional superconductivity under high pressure. CrAs starts superconducting at around 1.2 gigapascals (GPa), while MnP requires pressure as high as 8 GPa. This makes their experimental study incredibly challenging.

Now, in a recent study published in the Journal of the Physical Society of Japan, researchers reviewed the existing research on the magnetic properties of CrAs, MnP, and similar materials with the  MnP-type structure under high pressure to, understand how pressure influences superconductivity of these systems.

The review revealed that the magnetic properties of these materials are shaped by multiple exchange interactions. Both CrAs and MnP exhibit a double-helical spin structure at ambient pressure. At high pressures, both materials display quantum critical behavior, which may be key to their unconventional superconductivity. The presence of multiple exchange interactions in the superconducting phase of both materials is also important. However, despite having similar magnetic properties, other MnP-type materials do not exhibit superconductivity.

The study also reviewed recent advancements in hydrostatic pressure cells such as piston cylinder, Paris-Edinburgh, McWhan-type, cubic anvil, and diamond anvil cells, used for neutron scattering studies of these materials under high pressure.

These findings shed light on pressure-induced superconductivity in CrAs and MnP, paving the way to the development of more chromium and manganese based　superconductors. This, in turn, could lead to materials with higher transition temperatures or those capable of generating stronger magnetic fields, enhancing technologies like MRI machines and maglev trains.

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