Pressure-induced magnetization

Nikitin S.A., Tishin A.M., Kuz min M.D., Spichkin Yu.I. (1991) A pressure-induced magnetic phase transition in Y2Fci7 intermetallic compounds. Phys.Lett. A 153, 155-161. 

The work on iron-nickel alloys has described shock-compression measurements of the compressibility of fee 28.5-at. % Ni Fe that show a well defined, pressure-induced, second-order ferromagnetic to paramagnetic transition. From these measurements, a complete description is obtained of the thermodynamic variables that change at the transition. The results provide a more complete description of the thermodynamic effects of the change in the magnetic interactions with pressure than has been previously available. The work demonstrates how shock compression can be used as an explicit, quantitative tool for the study of pressure sensitive magnetic interactions. 

Fig. 5.16. The relative, shock-induced magnetization change is determined at a given pressure by the ratio of peak current to that at full magnetization change. Various sensitivities with pressure are indicated in agreement with static high pressure data. Offsets at zero magnetization change are typical and may be due to magnetic or mechanical effects (after Edwards [90E01]).

Raman spectroscopy is very useful in identifying vibration modes (phonons) in solids. This means that structural changes induced by external factors (such as pressure, temperature, magnetic fields, etc.) can be explored by Raman spectroscopy. It is also a very useful technique in chemistry, as it can be used to identify molecules and radicals. On many occasions, the Raman spectrum can be considered to be like a fingerprint of a substance. 

For ferrofluids, the usual form of the Bernoulli equation which relates the pressure of an incompressible liquid to its kinetic and potential energy must be modified to include the magnetic pressure induced by an applied magnetic field. The modified equation reads ... 

As a general empirical rule for HoNi2B2C samples, the appearance of reentrant behavior caused by stoichiometric effects, disorder, pressure, or magnetic field is always connected with a reduced value of Tc. Thus Schmidt (1997) could systematically reduce Tc and induce reentrant behavior in HoNi2B2C by the substitution of Ni by Co to a minor degree. An example for the influence of heat treatment is... 

TAS) energies or between pressure-induced electron delocalization and temperature-induced electron ionization, reflected on stabilities of phases and the phase boundaries. These pressure-temperature induced changes are unique, establishing an entirely different set of periodic behaviors in crystal stmcture and electronic and magnetic properties not found in the conventional periodic table. In return, this is what makes the Mbar chemistry" unique from any ambient-pressure combinatorial chemistry based on variation of chemical composition and temperature. New opportunities to discover interesting phenomena and exotic materials exist in both liquids and solids at high pressures. 

Above 130 kbar there is a phase change to a non-magnetic hexagonal phase which has a chemical isomer shift 0-17 mm s more negative than for the body-centred cubic a-iron [13, 15]. The relative line intensities are also affected by pressure due to a pressure-induced polarisation of the iron foil... 

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