Abstract
In this study, the synthesis of a novel ternary intermetallic compound Pr2Ni0.95Si2.95 forming in single phase only by deliberately introducing vacancies in Ni/Si site is reported. The detailed studies on dc magnetization, heat capacity, ac magnetization & associated dynamical scaling, different types of non-equilibrium dynamical behaviour, viz., magnetic relaxation behaviour as a function of wait time and temperature, aging phenomena, and magnetic memory effect firmly establish that the compound exhibits spin freezing behaviour below 3.3 K (Tf). However, below Tf, temperature dependence of ac susceptibility data exhibit an additional peak that shows reverse frequency dependence to that generally observed in a glassy system. The unusual bidirectional frequency dependence in a single magnetic system is of significant interest and rarely reported in literature. Competing exchange interaction arising from c/a ~ 1 and crystallographic randomness driven magnetic phase separation has been argued to be responsible for such observation. The reverse frequency shift of the low temperature peak has been described on the basis of a simple phenomenological model proposed in this work.
Highlights
A correlated magnetic spin system is called magnetically frustrated when it is unable to simultaneously minimize all its interaction energies between it’s ground state configuration of spins
We report the successful synthesis of a novel intermetallic compound Pr2Ni0.95Si2.95, which form in single phase only with defect crystal structure
It may be noted here that many similar R2TX3 type of compounds have been reported in literature to form along with a secondary phase which were of RT2X2 type[16], in contrast to PrNiSi2 found in our system
Summary
The single phase compound could be synthesized only by introducing defects in Ni and Si sites having the starting composition Pr2Ni0.95Si2.95 where all the peaks in the XRD pattern can be well indexed with space group P6/mmm [Fig. 2(b)]. Transmission Electron Microscopy (TEM) was carried out to investigate the nature of phase, composition and crystallinity of intermetallic compound Pr2Ni0.95Si2.95. Though some of the earlier reports yield superstructure formation in single crystalline R2TSi3 type of materials[19], no evidence of any such superstructure formation could be traced from the electron diffraction pattern in the defect structure compound Pr2Ni0.95Si2.95 [Fig. 3(b)].
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