Spin glass, single-ion and dense Kondo effects in La_1−xCe_xFePO

¹ Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China
² Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology Wuhan 430074, China
³ Department of Physics, Hangzhou Normal University - Hangzhou 310036, China
⁴ Zhejiang California International NanoSystems Institute, Zhejiang University - Hangzhou 310058, China

^(a) mpzslyk@gmail.com
^(b) zhuan@zju.edu.cn

Received: 3 June 2018
Accepted: 3 September 2018

Abstract

We investigated a series of La_1−xCe_xFePO , and constructed a rich phase diagram by transport, magnetic, and thermodynamic measurements. Upon Ce doping, superconductivity is suppressed and disappears near . For the broad doping region , the Ce moments behave as single-ion Kondo impurities. With further Ce doping, the system evolves into a coherent Kondo lattice, with the critical concentration far exceeding the percolation limit of for a two-dimensional square lattice. No long-range magnetic ordering is identified on this phase diagram, while short-range spin-glass behavior is suggested to coexist with the single-ion Kondo phase. Within the spin-glass phase, the dominant magnetic correlation is found to change from antiferromagnetic-like to ferromagnetic-like as Ce concentration increases. We discuss the results based on the disordered Kondo lattice model, and ascribe the phase diagram to the high frustration of the Ce moments introduced by the superexchange interactions bridged by O and P anions. Our work hence provides an intriguing platform to study the disordered Kondo effect in the high-frustration limit.