Spin flop 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. 

A material such as hematite, that can host a WF magnetic structure, also is able to host a classic AF structure with magnetic sublattices along a different crystalline axis. A spin flop transition, known as the Morin transition in hematite, can occur where the AF axis abruptly changes from one crystal orientation to another, at a certain transition temperature. Such spin flop transitions are sensitive to sample features such as impurity chemistry and particle size and shape, as discussed below (Dang et al. 1998). 

The worm and directed loop algorithms are applied when magnetic fields are present. Typical examples include the calculation of magnetization curves of quantum magnets [74], the determination of the first order nature of the spin flop transition in two dimensions [75] and the calculation of phase diagrams of dimerized quantum magnets in a magnetic field [76]. 

Fig. 4.13. Spectra of a single crystal of CsjFeCls. HjO at 42K. The applied field is directed along the magnetic easy axis, the a axis, and the gamma-ray beam is directed along the crystal c axis. At B= 1.25 T the antiferromagnetic axis is parallel to the field direction, at B= 1.30 T the spin flop is approximately half completed as indicated by the intensities of the Anti=0 lines and at 1.3ST the spin flop transition is complete with the antiferromagnetic axis now reoriented along the crystal c axis and parallel to the gamma-ray beam. In this configuration the Am/=0 lines vanish. (Johnson, 1985.)...

Fig. 63. Magnetization curves along each principal axis in the orthorhombic GdCuj compound at 1.3 K note the spin-flop transition along the b and c axes (after Takayanagi et al. 1989).

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