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Advisory Committee Chair

Wenli Bi

Advisory Committee Members

Esen E Alp

Yogesh Vohra

Document Type

Thesis

Date of Award

2021

Degree Name by School

Master of Science (MS) College of Arts and Sciences

Abstract

Eu(Fe0.75Ru0.25)2As2 is an intriguing system with unusual coexistence of superconductivity (TC≈23 K) and ferromagnetism (Tm≈20 K) and provides a unique platform to study of the nature of such coexistence. To establish a microscopic magnetic phase diagram of the recent doped 122-type ferromagnetic superconductor Eu(Fe0.75Ru0.25)2As2, time-resolved synchrotron Mössbauer experiments in 151Eu have been performed on a single crystalline sample under hydrostatic pressure and low temperatures. Upon compression, the magnetic ordering temperature first increases sharply from 20 K at ambient pressure to 53 K at 10 GPa. With further compression, the magnetic ordering temperature decreases and the magnetic order is fully suppressed above 25.2 GPa. X-ray absorption spectroscopy experiments at Eu’s L-3 edge were conducted to provide complimentary information on Eu’s valence state. Preliminary electrical resistivity measurements in diamond anvil cell have also been performed to probe the superconducting states under pressure. Evolution of the magnetic and valence with pressure will be discussed in detail.

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