Non-monotonic field dependence of Neel temperature in the quasi-2D magnet [Cu(HF{sub 2})(pyz){sub 2}]BF{sub 4}.
The measured thermodynamic phase diagram of the quasi-two-dimensional magnet [Cu(HF{sub 2})(pyz){sub 2}]BF{sub 4}(pyz=pyrazine=N{sub 2}C{sub 4}H{sub 4}) exhibits an unusual nonmonotonic dependence of the Neel temperature T{sub N} as a function of magnetic field H. The nonmonotonic behavior of T{sub N}(H) results from two competing effects induced by the field: while H suppresses the amplitude of the order parameter by polarizing the spins along a given direction, it also reduces the phase fluctuations by changing the order parameter space from the sphere S{sup 2} to the circle S{sup 1}. The latter effect dominates at low fields only if the system is close enough to its lower critical dimension (d{sub c} = 2), i.e., when fluctuations become important. Our theoretical results reproduce the measured phase diagram and demonstrate that this unusual effect is realized in [Cu(HF{sub 2})(pyz){sub 2}]BF{sub 4}.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC; NSF
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 961714
- Report Number(s):
- ANL/MSD/JA-61695
- Journal Information:
- Phys. Rev. B., Journal Name: Phys. Rev. B. Journal Issue: 2009 Vol. 79; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- ENGLISH
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