The field-induced first-order phase transition in $\left({\text{Er}}_{1-x}{\text{Y}}_x\right){\text{Co}}_2$ with the yttrium concentration $x=0.45$ is observed to be accompanied by a butterflylike behavior and significant irreversibility of the specific heat. The coefficient $\gamma$ of the $T$-linear specific heat decreases by $\sim 48\%$ under application and removal of a magnetic field up to 20 kOe. This behavior is attributed to the itinerant electron metamagnetism of $\text{Co}3d$ electrons. The isothermal magnetic entropy change $\Delta S_m$ in ${\text{Er}}_{0.55}{\text{Y}}_{0.45}{\text{Co}}_2$ includes a large contribution associated with spin fluctuations induced by the $f\text{−}d$ exchange interaction in the hybridized $3d\text{−}5d$-electron subsystem. These spin fluctuations are suggested to contribute substantially to the magnetocaloric effect of the $R{\text{Co}}_2$ type compounds. The maximal $\Delta S_m$ value observed for ${\text{ErCo}}_2$ just above the Curie temperature is ascribed to the closeness of the $T_{\text{C}}$ value to the spin-fluctuation temperature $T_{\text{sf}}$ of itinerant $\text{Co}3d$ electrons. The nonmonotonous change in $\Delta S_m$ with the Curie temperature of $R_{1-x}{R}_x^{\prime }{\text{Co}}_2$ compounds is explained by the temperature variation in the spin-fluctuation contribution to the magnetocaloric effect.

We present the results of measurements of low-temperature heat capacity, as well as electrical and magnetic properties of Heusler alloys Fe2VAl and Fe2CrAl prepared in different ways using various...

Here we study the influence of Al doping on the magnetization, heat capacity, and entropy change of La(Fe${}_{0.88}$Si${}_{0.12-x}$Al${}_x$)${}_{13}$ where $x$ $=$ 0, 0.048, and 0.081. When $x$ $=$ 0, the system shows a remarkably sharp heat capacity feature associated with spin fluctuations coincident with, but quite distinct from the latent heat spike of the first order paramagnetic to ferromagnetic phase transition. With the addition of Al the magnetic and calorimetric features become more distributed in field, suggesting that Al adds disorder to the system. For both finite $x$ compositions studied here, the latent heat disappears and the transition can be classified as second order. Although the entropy change associated with the transition is reduced once Al is substituted for Si, the adiabatic temperature change, $\Delta T_{\mathrm{ad}}$ is still significant. In La(${\mathrm{Fe}}_{0.88}{[\mathrm{Si}}_{0.12-x}{\mathrm{Al}}_x$)${}_{13}$ the balance between changes in the field dependence of the heat capacity with respect to overall $\Delta T_{\mathrm{ad}}$ gain is highlighted, showing that a small amount of Al doping clearly offers some advantage for application.

Magnetoresistivity features connected with the spin level coincidences under tilted fields in a ${\Gamma }_8$ conduction band of the HgTe quantum well were found to align along straight trajectories in a $(B_{\perp },B_{\left|\right|})$ plane between the field components perpendicular and parallel to the layer, meaning a linear spin polarization dependence on a magnetic field. Among the trajectories is a noticeable set of lines descending from a single point on the $B_{\left|\right|}$ axis, which is shown to yield a field of the full spin polarization of the electronic system, in agreement with the data on the electron redistribution between spin subbands obtained from Fourier transforms of oscillations along circle trajectories in the $(B_{\perp },B_{\left|\right|})$ plane and with the point on the magnetoresistivity under pure $B_{\left|\right|}$ separating a complicated weak field dependence from the monotonous one. The whole picture of coincidences is well described by the isotropic $g$ factor, although its value is twice as small as that obtained from oscillations under pure perpendicular fields. The discrepancy is attributed to different manifestations of spin polarization phenomena in the coincidences and within the exchange-enhanced spin gaps. In the quantum Hall range of $B_{\perp }$, the spin polarization manifests in anticrossings of magnetic levels, which were found to depend dramatically nonmonotonously on $B_{\perp }$.