Magnetic Properties of CuF2

Abstract

We have measured the moment of a pressed powder sample of monoclinic CuF2 from 4.2° to 300°K in fields to 25 kOe. χ(T) indicates an AFM transition at TN=69°K, and analysis gives ḡ≈2.3 and Θ≈−200°K. TN and Θ are consistent with magnetic ordering of the first kind with AFM exchange interactions J1(corner-bc)≈34°K and J2≈22°K. Weak ferromagnetism of anisotropic exchange origin is expected on the grounds of symmetry; the measured ferromagnetic moment is σ0≈1 G cm3/mole, corresponding to a canting angle φ≈0.01°. Assuming magnetic dipolar anisotropy and estimating principal axes and values for the anisotropic g tensor, we find the spin axis to be about 2° from c and 99° from a in the ac plane with anisotropy field HA∼2000 Oe, and the weak moment to be parallel to the monoclinic axis b with canting field HDM∼1000 Oe. Pseudodipolar anisotropy may be expected to change the orientation, but not the order of magnitude of these fields. The uniform mode AFM resonances are not degenerate in general, but both would be expected to occur at v/c∼9 cm−1 using these values.

The Jahn-Teller Distortion at High Pressure: The Case of Copper Difluoride

“…This structure, shown in Figure 1b, can be also transformed to a P2 1 /c setting ( Figure 1c) which more clearly illustrates the presence of puckered sheets of [CuF 4/2 ] stoichiometry. These sheets host a relatively strong antiferromagnetic (AFM) interaction between the neighboring Cu 2+ sites [56], which together with a weak ferromagnetic (FM) inter-layer coupling leads to a spin-canted 2D AFM state below 70 K [46,57,58]. Hereinafter when referring to the ambient pressure rutile-type structure of CuF 2 we will use the P2 1 /c setting.…”

Magnetic coupling in the weak ferromagnetCuF2

“…The experimentally determined structure parameters 26 have been used without modification, and are reported in Table I. The crystal structure was determined at several temperatures and we have chosen the parameters corresponding to 77.3 K, a temperature close to the Néel temperature of 69 K. 27 The CuF 2 structure is commonly described as a distorted rutile structure, a structure adopted by many transition-metal oxides and halides. It is formed by octahedra of fluorine surrounding Cu cations, each fluorine anion being threefold coordinated to Cu, Fig.…”

A Unique Two‐Dimensional Silver(II) Antiferromagnet Cu[Ag(SO4)2] and Perspectives for Its Further Modifications

“…In CuAg(SO 4 ) 2 there is no center of inversion between the two cations so DM interaction is allowed in general, and then it is a stronger effect than the symmetric exchange anisotropy [46] . Comparison of Cu 2+ and Ag 2+ compounds with similar structures and the same ligands, CuF 2 and AgF 2 , reveal that the higher T t is observed for the latter, due to both the stronger intra‐sheet and inter‐sheet SE [2,43–45] . Also, a larger canting angle has been reported for Ag 2+ (0.5°) [1] in AgF 2 than Cu 2+ in CuF 2 (0.1°) [43] .…”