Composite materials containing hydrogenated La(Fe,Mn,Si) sub(13) powder and 5 wt.% of polymer binder have very good magnetocaloric properties and can be machined in a heat exchanger. These heat ...exchangers have to fulfill certain requirements regarding their mechanical and chemical stability. In this paper, we have investigated the magnetocaloric properties of thin composite plates produced by two different methods: 1) wire saw cutting and 2) cold rolling. The flexural strength of the plates was investigated by three-point bending method. Furthermore, the corrosive behavior of the plates in different heat transfer fluids was investigated. Finally, the adiabatic temperature change and the magnetic entropy change of the plates were observed over a seven-month period in order to evaluate their applicability in a real device.
Composite materials containing hydrogenated La(Fe,Mn,Si)13 powder and 5 wt.% of polymer binder have very good magnetocaloric properties and can be machined in a heat exchanger. These heat exchangers ...have to fulfill certain requirements regarding their mechanical and chemical stability. In this paper, we have investigated the magnetocaloric properties of thin composite plates produced by two different methods: 1) wire saw cutting and 2) cold rolling. The flexural strength of the plates was investigated by three-point bending method. Furthermore, the corrosive behavior of the plates in different heat transfer fluids was investigated. Finally, the adiabatic temperature change and the magnetic entropy change of the plates were observed over a seven-month period in order to evaluate their applicability in a real device.
Intrinsic magnetic properties of (Fe 1-x Co x ) 2 B (x = 0.20, 0.25, 0.30, 0.35) alloys have been studied on single crystals. Temperature dependence of both magnetocrystalline anisotropy constant K 1 ...and spontaneous magnetization M s has been determined from magnetization isotherms measured between 10 and 1000 K. The highest anisotropy constant K 1 was obtained at x = 0.25, K 1 = 494 kJ/m 3 at T = 10 K. The Curie temperature decreased from 966 to 930 K as x increased from 0.2 to 0.35.
Magnetic refrigeration is an upcoming technology that could be an alternative to the more than 100‐year‐old conventional gas–vapor compression cooling. Magnetic refrigeration might answer some of the ...global challenges linked with the increasing demands for readily available cooling in almost every region of the world and the global‐warming potential of conventional refrigerants. Important issues to be solved are, for example, the required mass and the ecological footprint of the rare‐earth permanent magnets and the magnetocaloric material, which are key parts of the magnetic cooling device. The majority of existing demonstrators use Nd–Fe–B permanent magnets, which account for more than 50% of the ecological footprint, and Gd, which is a critical raw material. This work shows a solution to these problems by demonstrating the world's first magnetocaloric demonstrator that uses recycled Nd–Fe–B magnets as the magnetic field source, and, as a Gd replacement material, La–Fe–Mn–Si for the magnetocaloric heat exchanger. These solutions show that it is possible to reduce the ecological footprint of magnetic cooling devices and provides magnetic cooling as a green solid‐state technology that has the potential to satisfy the rapidly growing global demands.
A magnetic cooling device with recycled Nd–Fe–B magnets and the “free rare‐earth” magnetocaloric material La–Fe–Si is used to prove that green magnetic cooling is possible. The recycled magnets provide a magnetic field of up to 1.15 T and a temperature span of 25 K is achieved with a five‐stage active magnetic regenerator made from La–Fe–Si.
We have investigated thermal conductivities (κ) of polycrystalline Eu1–xAxTiO3 (A = Ca, Sr, Ba, 0 ≤ x ≤ 0.8) bulk materials in the temperature range of ∼ 2 K <T < 1173 K. The EuTiO3 demonstrates ...anomalous glass-like κ(T) behavior at low temperatures. Partial substitutions with Sr2+ and Ba2+ do not cause a significant change in the κ(T) behavior, while a κ(T) peak, which looks like a manifestation of a typical crystalline solid, appears only in the Ca-substituted samples with an orthorhombic structure when x ≥ 0.4. After excluding the magnetic effects on κ and discussing the possible phonon scattering mechanisms in depth, together with heat capacity Cp measurements and high-resolution X-Ray diffraction characterization, we find that the unusual low κ at low temperatures is attributed to resonant scattering induced by the intrinsic disordered local structure and lattice instability in EuTiO3. Due to the different lattice dynamics of ATiO3, the lattice structure of Eu1–xCaxTiO3 can be regarded as formed by a part-soft (from EuTiO3) part-rigid (from CaTiO3) sublattice. The anomalous κ(T) behavior of Eu1–xCaxTiO3 results from the combined effect of phonon transport between the normal phononic heat transport in the rigid sublattice and the strong damping of heat conduction in the soft sublattice.
The evolution of magnetic anisotropy in bcc Fe as a function of interstitial boron atoms was investigated in thin films grown by molecular beam epitaxy. The thermodynamic nonequilibrium conditions ...during film growth allowed one to stabilize an interstitial boron content of about 14at.% accompanied by lattice tetragonalization. The c/a ratio scaled linearly with the boron content up to a maximum value of 1.05 at 300∘C substrate growth temperature, with a room-temperature magnetization of. In contrast to nitrogen interstitials, the magnetic easy axis remained in-plane with an anisotropy of approximately −5.1×106erg/cm3. Density functional theory calculations using the measured lattice parameters confirm this value and show that boron local ordering indeed favors in-plane magnetization. Given the increased temperature stability of boron interstitials as compared to nitrogen interstitials, this study will help to find possible ways to manipulate boron interstitials into a more favorable local order.
Magnetic nanopatterns were successfully created in FeRh thin film deposited on MgO (100) substrates. Silica and polystyrene spherical masks, nominally 500 and 1000 nm in diameter, respectively were ...applied on the surface of the sample in order to locally shadow the film against the effect of 110 keV energy neon-ion irradiation with fluences of 1015 and 1016 ions/cm2. Such nanosphere-lithography technique allows for projecting the mask geometry on the magnetic structure of the FeRh film. Conversion-electron Mössbauer spectroscopy and magnetic force microscopy were used to determine the ferromagnetic ratio and the magnetic pattern in the samples, and nuclear resonance scattering of synchrotron radiation was applied to obtain the in-depth magnetic profile. From the results obtained, the possible three-dimensional (3D) structure of the created individual magnetic domains was also constructed. Overall, the great customizability of the presented nanosphere-lithography technique in FeRh thin film provides opportunities for developing cutting-edge spintronic applications.
It has come to the attention of IOP Publishing that this article should not have been submitted for publication owing to its substantial replication of an earlier paper G M Schmiedeshoff et al 2006 ...Versatile and compact capacitive dilatometer Rev. Sci. Instrum. 77 123907 This article was submitted by I Radulov without the knowledge of the other authors. Retraction published: 16 July 2013
In the present article we want to report about our miniature capacitance dilatometer developed for magnetostriction and thermal expansion measurements. The dilatometer is foreseen to be used on ...millimeter-sized single crystalline samples in the temperature range 2 – 320K. The dilatometer main body is produced of brass and is mounted in low vacuum. The capacitance was measured with a digital, self-balancing, three terminal, commercial capacitance bridge operating in the frequency range 50 Hz − 20 kHz. The temperature was determined using commercial resistive thermometers Cernox BG 1030 and Cryo-con Model 44 Temperature controller.
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