Abstract

In this work, a systematic study of Cu(NO3)2·2.5 H2O (copper nitrate hemipentahydrate, CN), an alternating Heisenberg antiferromagnetic chain model material, is performed with multi-technique approach including thermal tensor network (TTN) simulations, first-principles calculations, as well as magnetization measurements. Employing a cutting-edge TTN method developed in the present work, we verify the couplings J = 5.13 K, α = 0.23(1) and Landé factors g∥= 2.31, g⊥ = 2.14 in CN, with which the magnetothermal properties have been fitted strikingly well. Based on first-principles calculations, we reveal explicitly the spin chain scenario in CN by displaying the calculated electron density distributions, from which the distinct superexchange paths are visualized. On top of that, we investigated the magnetocaloric effect (MCE) in CN by calculating its isentropes and magnetic Grüneisen parameter. Prominent quantum criticality-enhanced MCE was uncovered near both critical fields of intermediate strengths as 2.87 and 4.08 T, respectively. We propose that CN is potentially a very promising quantum critical coolant.

Highlights

  • Heisenberg spin chains and nets, owing to their strong quantum fluctuations and correlation effects, can accommodate plentiful interesting quantum phases like topological spin liquids[1,2], unconventional excitations like anyon-type quasi particles[3], and inspiring behaviors like Bose- Einstein condensation in magnets[4], which continues stimulating both condensed matter theorists and experimentalists

  • Sharples et al realized temperatures as low as ∼​200 mK using the enhanced magnetocaloric effect (MCE) of a molecular quantum magnet[40], and Lang et al experimentally studied a spin-1/2 Heisenberg antiferromagnetic chain material [Cu(μ-C2O4)(4-aminopyridine)2(H2O)]n (CuP, for short)[48], and demonstrated this quantum critical coolant is a perfect alternative to standard adiabatic dimagnetization refrigerant (ADR) salts, due to its wider operating temperature range, longer holding time and higher efficiency[49]

  • Through thermal tensor network (TTN) simulations, we show that copper nitrate (CN) has large entropy change and pronounced peaks in Grüneisen parameter around quantum critical points (QCPs) at low temperatures, and the calculated adiabatic temperature changes can fit very well to the previously measured isentropes, revealing that CN may be an ideal quantum critical refrigerant

Read more

Summary

Introduction

Heisenberg spin chains and nets, owing to their strong quantum fluctuations and correlation effects, can accommodate plentiful interesting quantum phases like topological spin liquids[1,2], unconventional excitations like anyon-type quasi particles[3], and inspiring behaviors like Bose- Einstein condensation in magnets[4], which continues stimulating both condensed matter theorists and experimentalists. What is more, these low-dimensional systems, which at a first glance are of purely academic interest, can have their experimental realizations.

Methods
Results
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call