Complex magnetic properties associated with competing local and itinerant magnetism in {text {Pr}}_2 {text {Co}}_{0.86} {text {Si}}_{2.88}

Mily Kundu,Maxim Avdeev,Stephen Cottrell,Devashibhai Adroja,Chandan Mazumdar,N Lakshminarasimhan,Durga Paudyal,Renu Choudhary,Santanu Pakhira,R Ranganathan

doi:10.1038/s41598-021-90751-0

Abstract

Ternary intermetallic compound {text {Pr}}_2 {text {Co}}_{0.86} {text {Si}}_{2.88} has been synthesized in single phase and characterized by x-ray diffraction, scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDX) analysis, magnetization, heat capacity, neutron diffraction and muon spin rotation/relaxation (muSR) measurements. The polycrystalline compound was synthesized in single phase by introducing necessary vacancies in Co/Si sites. Magnetic, heat capacity, and zero-field neutron diffraction studies reveal that the system undergoes magnetic transition below sim4 K. Neutron diffraction measurement further reveals that the magnetic ordering is antiferromagnetic in nature with an weak ordered moment. The high temperature magnetic phase has been attributed to glassy in nature consisting of ferromagnetic clusters of itinerant (3d) Co moments as evident by the development of internal field in zero-field muSR below 50 K. The density-functional theory (DFT) calculations suggest that the low temperature magnetic transition is associated with antiferromagnetic coupling between Pr 4f and Co 3d spins. Pr moments show spin fluctuation along with unconventional orbital moment quenching due to crystal field. The evolution of the symmetry and the crystalline electric field environment of Pr-ions are also studied and compared theoretically between the elemental Pr and when it is coupled with other elements such as Co. The localized moment of Pr 4f and itinerant moment of Co 3d compete with each other below sim20 K resulting in an unusual temperature dependence of magnetic coercivity in the system.

Highlights

Ternary intermetallic compound Pr2Co0.86Si2.88 has been synthesized in single phase and characterized by x-ray diffraction, scanning electron microscopy with energy dispersive x-ray spectroscopy (SEMEDX) analysis, magnetization, heat capacity, neutron diffraction and muon spin rotation/relaxation measurements
It was reported that the arc furnace synthesis of these R2TX3 type of polycrystalline compounds often results in an additional secondary phase, either of RT2X2 type[24,25] or RTX2 type[2]
Susceptibility, heat capacity measurements and density-functional theory (DFT) calculations suggest a Pr-Co magnetic ordering below 4 K but with weak ordered moment as revealed through neutron diffraction measurement

Summary

Introduction

Ternary intermetallic compound Pr2Co0.86Si2.88 has been synthesized in single phase and characterized by x-ray diffraction, scanning electron microscopy with energy dispersive x-ray spectroscopy (SEMEDX) analysis, magnetization, heat capacity, neutron diffraction and muon spin rotation/relaxation ( μSR) measurements. Even a slight variation in composition are known to alter the magnetic property significantly as seen in the ac susceptibility data of polycrystalline Pr2Ni0.95Si2.95 that exhibits an additional peak showing a reverse frequency dependence[3] in contrast to that generally observed in a spin-glass system, but is absent in single crystalline full stoichiometric Pr2NiSi320 In such a magnetically complex system, one may have an additional magnetic interaction, by introducing a moment carrying element in the transition metal site. The presence of the Co-moment could be an additional source of magnetic interaction that may allow us to investigate any complex phenomena associated with competing magnetic interactions between localized (4f) and local/itinerant (3d) moment in R2CoSi3 series of compounds These Co-based compounds, have been reported to crystallize in a superstructure form ( U2RuSi3-type) of the basic AlB2-type crystal structure, where the Co and Si atoms are placed in a regular order having separate Wyckoff p ositions[21]. To understand the origin of this unusual anomaly, we have utilized the above mentioned experimental techniques as well as theoretical calculations and present our results depicting a competing local and itinerant moment picture

Methods

Results

Conclusion