Spin-flop

MM (metamagnet), AF (antiferromagnet), SF (spin-flop), Frust. Mgn. (frustrated magnet) and FIM (ferrimagnet) ... 

Table 2 Evolution of the structural and magnetic characteristics of the [Cp2Mo(dmit)]X salts (X = PF6 , Asly,, Shly, ) with the anion size (BSf stands for the spin-flop field in AF state)...

A three-dimensional set of intermolecular interactions is further confirmed by the observation of a transition to an antiferromagnetic ground state in both radical complexes, at a Neel temperatures of 8 (Mo) and 4.5 K (W), in accordance with the difference of Curie-Weiss temperatures between both complexes. Note also the spin-flop field in the antiferromagnetic state, found at 5.5 kG in [Cp M(dmit)2] and at 8 kG in [Cp W(dmit)2] , a consequence of the stronger spin orbit coupling in the latter. 

OX or OY axis [11], The magnetic ordered phase T45 in the Cui xZnxGe02 realizes at H < Hsj, and at II > IIsj the spin-flop phase I47 takes place, because OX axis is the second easy axis [9], When the magnetic field becomes H Hex Jc the second order phase transition... 

It should be taken into account that even while the spin-flop transition possesses the character of a 1-st order phase transition at a precise alignment of the magnetic field along the z-axis, the character of the 1-st order transition is lost when h tilts away from the z-axis by an angle larger than a certain critical value ipc. The critical angle value is deter-... 

Magnetic properties of antiferromagnetic MnF2 in the vicinity of the spin-flop transition. Experimental results and discussion [1-3]... 

The spin-flop transition in M11F2 is of first order at ip < -i/y 30 only. Extremely fine orientation of the magnetic field relative to the crystal axis should be achieved (as the permitted error should not exceed several angular minutes). For this reason the solenoid is mounted on a separate plate, and its slope is varied by 4 micrometer screws. 

At small angles of the field H tilt away from the fourfold crystal axis z (ip C 1), though larger than the critical value ipc 30, a rapid increase of Mz is observed at the spin-flop transition, while Mj passes through a maximum (Fig. 7). It means, that the increase of the magnetization Mz is concurrent with a turn of M to the angle A0 = 7t/2. The shape... 

The intermediate state in MnF2 in the neighbourhood of the spin-flop transition was studied by means of nuclear magnetic resonance [5] and antiferromagnetic resonance [12], [14]. 

The domain structure, which appears in MnF2 at the spin-flop transition illustrates a general thermodynamic law of intermediate state formation in the process of first-order phase transitions, induced by a magnetic field, and under the condition that the surface energy of the interface boundary (a > 0) is positive. 

K.L. Dudko, V.V. Eremenko, V.M. Fridman, Magnetization jumps and domain structure of manganise fluoride at sublattice spin-flopping. Sov. Phys.-JETP, 61, No 4, 1553-1563 (1971)... 

A.R. King, D. Paquette, Spin-flop domains in MnF2. Phys. Rev. Lett., 30,... 

S.M. Rezende, A.R. King, R.M. White, J.P. Timble, Stability limit at the antiferromagnetic phase near spin-flop boundary in MnF2. Phys. Rev. B, 16, No 3, 1126-1131 (1977)... 

J.S. Jacobs, Spin-flopping in MnF2 by high magnetic fields. J. Appl. Phys., 32, 61S-62S (1961)... 

In the first two chapters, the different theories explaining low-dimensional magnetic behavior will be briefly considered and also the available techniques. Then, the most important part (Chap. 3) will deal with fluorinated materials showing low-dimensional magnetism in structures characterized by a 3-D crystallographic arrangement of MF6 octahedra, layers, chains and rings. Spin-flop and zero-point spin-reduction will be also considered, since fluorides provide in these domains most of the conclusive examples. 

Fluorides with a BaMnF4 Structure. Two fluorides belong to this family BaMnF4 and BaNiF4. BaMnF4114 has been studied by Holmes et al.122. They found an exchange constant of — 2.72 K and a spin-flop phenomenon for He = 10.4 kOe. The anisotropy is described by the law H2 = 2HAHE (E - where Xf/Xi 0.047. The Neel tempera-... 

In contrast to the Ising model, spin-flop is observed in Heisenberg systems over a large range of applied fields and temperatures. 

When increasing the value of H, the moments gradually rotate towards the applied field direction and when H = Hc, they are parallel to the field. In the molecular field model, the spin-flop is a first-order transition and the spin flop 5 paramagnetic transition a second-order process. Between HSF and Hc magnetization increases linearly with H M/Ms = H (2HE - Ha) where Ms is the saturation magnetization of a sublattice (Ms = A NgMBS). At T = 0 K, the critical field can be written as HSF = [2HE HA/(1 - a)]1/2... 

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