Pressure and magnetic field effects on a quasi-2D spin-1/2 Heisenberg antiferromagnet

Abstract

Cu(pz)2(ClO4)2 (with pz denoting pyrazine, C4H4N2) is among the best realizations of a two-dimensional spin-1/2 square-lattice antiferromagnet. Below T_N = 4.21 K, its weak interlayer couplings induce a 3D magnetic order, strongly influenced by external magnetic fields and/or hydrostatic pressure. Previous work, focusing on the [H, T] phase diagram, identified a spin-flop transition, resulting in a field-tunable bicritical point. However, the influence of external pressure has not been investigated yet. Here we explore the extended [p, H, T] phase diagram of Cu(pz)2(ClO4)2 under pressures up to 12 kbar and magnetic fields up to 7.1 T, via magnetometry and 35Cl nuclear magnetic resonance (NMR) measurements. The application of magnetic fields enhances T_XY , the crossover temperature from the Heisenberg to the XY model, thus pointing to an enhancement of the effective anisotropy. The applied pressure has an opposite effect [dT_N/dp = 0.050(8) K/kbar], as it modifies marginally the interlayer couplings, but likely changes more significantly the orbital reorientation and the square-lattice deformation. This results in a remodeling of the effective Hamiltonian, whereby the field and pressure effects compensate each other. Finally, by comparing the experimental data with numerical simulations we estimate T_BKT, the temperature of the Berezinskii-Kosterlitz-Thouless topological transition and argue why it is inaccessible in our case.

arXiv comment7 pages, 9 figures

References in corpus (11)

• The ALPS project release 2.0: Open source software for strongly correlated systems
• Quantum magnetism and criticality
• Neel Temperature of Quasi-Low-Dimensional Heisenberg Antiferromagnets
• Asymptotic scaling of the square lattice quantum Heisenberg antiferromagnet
• On the self-consistent spin-wave theory of layered Heisenberg magnets
• Magnetic order in the S=1/2 two-dimensional molecular antiferromagnet, copper pyrazine perchlorate Cu(Pz)_2(ClO_4)_2
• Detection of XY behaviour in weakly anisotropic quantum antiferromagnets on the square lattice
• The Two-Dimensional Square-Lattice S=1/2 Antiferromagnet Cu(pz)${}_2$(ClO${}_4$)${}_2$
• 2D XY Behavior observed in quasi-2D quantum Heisenberg antiferromagnets
• Spin polarization of the magnetic spiral in NaCu_2O_2, as seen by NMR
• Switching of anisotropy and phase diagram of a Heisenberg square lattice S=1/2 antiferromagnet Cu(pz)2(ClO4)2

Cited by in corpus (3)

• The princess and the pea: on the outsized role of inter-layer ligands in copper-pyrazine antiferromagnets
• Anisotropic XY antiferromagnets in a field
• Room-temperature structural phase transition in the quasi-2D spin-1/2 Heisenberg antiferromagnet Cu(pz)${}_2$(ClO${}_4$)${}_2$