# Magnetization of potassium doped p-terphenyl and p-quaterphenyl by high pressure synthesis

## TL;DR

This study reports high-pressure synthesis of potassium-doped p-terphenyl and p-quaterphenyl, observing magnetic transitions near 125 K suggestive of possible superconductivity, but with very small diamagnetic volume and ambiguous evidence.

## Contribution

First demonstration of potassium doping in p-terphenyl and p-quaterphenyl via high-pressure synthesis showing magnetic transitions near 125 K.

## Key findings

- Magnetic transitions at ~125 K observed in doped samples.
- Weak ferromagnetic background affects magnetization measurements.
- Small estimated diamagnetic volume (~0.0427%) suggests limited superconductivity evidence.

## Abstract

By using high pressure synthesis method, we have fabricated the potassium doped para-terphenyl. The temperature dependence of magnetization measured in both zero-field-cooled and field-cooled processes shows step like transitions at about 125 K. This confirms earlier report about the possible superconductivity like transition in the same system. However, the magnetization hysteresis loop exhibits a weak ferromagnetic background. After removing this ferromagnetic background, a Meissner effect like magnetic shielding can be found. A simple estimate on the diamagnetization of this step tells that the diamagnetic volume is only about 0.0427% at low temperatures, if we assume the penetration depth is much smaller than the size of possible superconducting grains. This magnetization transition does not shift with magnetic field but is suppressed and becomes almost invisible above 1.0 T. The resistivity measurements are failed because of an extremely large resistance. By using the same method, we also fabricated the potassium doped para-quaterphenyl. A similar step like transition at about 125 K was also observed by magnetization measurement. Since there is an unknown positive background and the diamagnetic volume is too small, it is insufficient to conclude that this step is derived from superconductivity although it looks like.