There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The recent literature concerning the magnetocaloric effect (MCE) has been reviewed. The MCE properties have been compiled and correlations have been made comparing the behaviours of the different families of magnetic materials which exhibit large or unusual MCE values. These families include: the lanthanide (R) Laves phases (RM2, where M = Al, Co and Ni), Gd5(Si1−xGex)4 ,M n(As1−xSbx), MnFe(P1−xAsx), La(Fe13−xSix) and their hydrides and the manganites (R1−xMxMnO3, where R = lanthanide and M = Ca, Sr and Ba). The potential for use of these materials in magnetic refrigeration is discussed, including a comparison with Gd as a near room temperature active magnetic regenerator material. (Some figures in this article are in colour only in the electronic version)

https://iopscience.iop.org/article/10.1088/0034-4885/68/6/R04/pdf

Recent developments in magnetocaloric materials

In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Surface plasmons (SPs) are coherent oscillations of conduction electrons on a metal surface excited by electromagnetic radiation at a metal -dielectric interface. The growing field of research on such light -metal interactions is known as ‘plasmonics’. 1-3 This branch of research has attracted much attention due to its potential applications in miniaturized optical devices, sensors, and photonic circuits as well as in medical diagnostics and therapeutics. 4-8

Nanostructured plasmonic sensors.

Review of the magnetocaloric effect in manganite materials

The giant magnetoimpedance (GMI) effect has been measured in Co 83.2 B 3.3 Si 5.9 Mn 7.6 amorphous microwire as a function of direct current (dc)-biased current and measuring frequency, f . The GMI profile has a single peak for f ⩽5 MHz, and two peaks at higher frequency. The maximum GMI ratio increases continuously with frequency up to 45% at 10 MHz. The influence of superimposed dc biasing is shown to result in asymmetrical GMI as well as in a shift of the axial hysteresis loop. Both effects are interpreted in terms of the relative contribution of domain wall and rotational processes to the transverse susceptibility.

Bias-current effect on giant magnetoimpedance in Co-based amorphous microwire

Spin wave stiffness constants of amorphous Fe-Zr-B-Nb alloys

Magnetic Entropy Change in Ba_1.9La_0.1FeMoO_6 with the Sintering Temperature

The critical behavior around the paramagnetic-ferromagnetic phase transition in perovskite manganites Nd0.5Sr0.5Mn1-xCoxO3( x = 0.03 and 0.05) has been studied in detail by using various techniques, such as the modified Arrott plot and critical isotherm analysis. Basing on the modified Arrott plot method, we obtained the critical parameters of TC ≈ 234.3 K, β = 0.414 ±0.047 and γ = 1.488 ±0.312 for x = 0.03, and TC ≈ 221.9 K, β = 0.450 ±0.10 and γ = 1.113 ±0.033 for x = 0.05. The determined values of the critical exponents are in between those expected for the 3-D Heisenberg and mean-field models. With these values, isothermal magnetization data of the samples around TC fall into two branches of a universal function M(H, e) = |e|β f± (H/|e|β+ γ), where e = (T-TC)/TC is the reduced temperature, f+ for T > TC and f for . This proves that the critical parameters determined are reliable and in accordance with the scaling hypothesis. Our results also demonstrate an existence of short-range ferromagnetic order in Nd0.5Sr0.5Mn1-xCoxO3. Particularly, the Co doping at high concentrations has a tendency leading to long-range ferromagnetic order.

Seong-Cho Yu

Papers

Bias-current effect on giant magnetoimpedance in Co-based amorphous microwire

Spin wave stiffness constants of amorphous Fe-Zr-B-Nb alloys

Magnetic Entropy Change in Ba_1.9La_0.1FeMoO_6 with the Sintering Temperature

Critical Behavior in Double-Exchange Ferromagnets ${\hbox{Nd}}_{0.5}{\hbox{Sr}}_{0.5}{\hbox{Mn}}_{1 \hbox{-} x}{\hbox{Co}}_{x}{{\hbox{O}}_3}$

Magnetic characteristics of La-deficient manganate single crystals