Magnetocaloric effect from indirect measurements: Magnetization and heat capacity
TL;DR: In this article, an approach to calculate the magnetocaloric effect from the combined heat capacity and magnetization data is proposed, based on the assumption that heat capacity is magnetic-field independent.
Abstract: Accurate values for the magnetocaloric effect can be obtained from both magnetization and heat-capacity data. A reliable estimate of the experimental errors in the calculated magnetocaloric effect can be made from the known experimental errors of the measured physical properties. Attempts in the past to simplify the basic thermodynamic relation to allow the calculation of the adiabatic temperature change from the heat capacity at constant field and the magnetic entropy change calculated from the magnetization data fail because the assumption that heat capacity is magnetic-field independent is erroneous. A suitable approach to carry out these calculations from the combined heat capacity and magnetization data is suggested.
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TL;DR: The recent literature concerning the magnetocaloric effect (MCE) has been reviewed and correlations have been made comparing the behaviours of the different families of magnetic materials which exhibit large or unusual MCE values.
Abstract: 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)
3,002 citations
TL;DR: The magnetocaloric effect and its most straightforward application, magnetic refrigeration, are topics of current interest due to the potential improvement of energy efficiency of cooling and temperature control systems, in combination with other environmental benefits associated to a technology that does not rely on the compression/expansion of harmful gases.
941 citations
TL;DR: In this paper, a review of the magnetocaloric response of materials for magnetic refrigeration close to room temperature is presented, focusing on the main families of materials suitable for this application and the procedures proposed to predict their response.
Abstract: In the past 20 years, there has been a surge in research on the magnetocaloric response of materials, due mainly to the possibility of applying this effect for magnetic refrigeration close to room temperature. This review is devoted to the main families of materials suitable for this application and to the procedures proposed to predict their response. Apart from the possible technological applications, we also discuss the use of magnetocaloric characterization to gain fundamental insight into the nature of the underlying phase transition.
910 citations
TL;DR: The magnetocaloric effects of Ni-Mn-based Heusler alloys are surveyed and their relation with the magnetic shape-memory and magnetic superelasticity reported in these materials are discussed.
Abstract: Magnetic Heusler alloys which undergo a martensitic transition display interesting functional properties. In the present review, we survey the magnetocaloric effects of Ni-Mn-based Heusler alloys and discuss their relation with the magnetic shape-memory and magnetic superelasticity reported in these materials. We show that all these effects are a consequence of a strong coupling between structure and magnetism which enables a magnetic field to rearrange martensitic variants as well as to provide the possibility to induce the martensitic transition. These two features are respectively controlled by the magnetic anisotropy of the martensitic phase and by the difference in magnetic moments between the structural phases. The relevance of each of these contributions to the magnetocaloric properties is analysed.
886 citations
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01 Jan 1965
TL;DR: In this paper, the authors present a review of the properties of the magnetic field and its properties in terms of properties such as: 1. The magnetic field, the magnetization vector, the Langevin Formula for Diamagnetic Susceptibility, and the magnetic shell.
Abstract: 1. The Magnetic Field. 1. Historical. 2. The Magnetic field Vector H. 3. The Magnetization Vector M. 4. Magnetic Induction, the Vector B. 5. The Demagnetization Factor D. 6. Energy of Interaction. 7. Magnetic Effects of Currents. The Magnetic Shell. Faradaya s Law. 8. Maxwella s and Lorentza s Equations. 9. The Magnetic Circuit. 10. Dipole in a Uniform Field. 2. Diamagnetic and Paramagnetic Susceptibilities. 1. Introduction. 2. Review of Quantum Mechanical and Other Results. Diamagnetism. 3. The Langevin Formula for Diamagnetic Susceptibility. 4. Susceptibility of Atoms and Ions. 5. Susceptibility of Molecules. Paramagnetism. 6. Curiea s Law. 7. Theoretical Derivations of Curiea s Law. 8. Quantum Mechanical Treatment. 9. Susceptibility of Quasi--free Ions: the Rare Earths. 10. The Effect of the Crystalline Field. 11. The Iron Group Salts. 12. Covalent Binding and the 3d, 4d, 5d, and 5f--6d Transition Groups. 13. Saturation in Paramagnetic Substances. 14. Paramagnetic Molecules. 15. Paramagnetic Susceptibility of the Nucleus. 3. Thermal, Relaxation, and Resonance Phenomena in Paramagnetic Materials. 1. Introduction. Thermal Phenomena. 2. Summary of Thermodynamic Relationships. 3. The Magnetocaloric Effect: The Production and Measurement of Low Temperatures. Paramagnetic Relaxation. 4. The Susceptibility in an Alternating Magnetic Field. 5. Spin--Lattice Relaxation. 6. Spin--spin Relaxation. Paramagnetic Resonance. 7. Conditions for Paramagnetic Resonance. 8. Line Widths: the Effect of Damping. 9. Fine and Hyperfine Structure: the Spin--Hamiltonian. 10. The Spectra of the Transition Group Ions. The 3d group ions. Covalent binding and the 3d, Ad, 5d, and 5f--6d groups. 4/rare earth ions in salts. Transition ions in various host lattices. 11. The Spectra of Paramagnetic Molecules and Other Systems. Paramagnetic gases. Free radicals. Donors and acceptors in semiconductors. Traps, F--centers, etc. Defects from radiation damage. 12. The Three--Level Maser and Laser. 4. Nuclear Magnetic Resonance. 1. Introduction. 2. Line Shapes and Widths. 3. Resonance in Nonmetallic Solids. 4. The Influence of Nuclear Motion on Line Widths and Relaxations. 5. The Chemical Shift: Fine Structure. 6. Transient Effects: the Spin--Echo Method. 7. Negative Temperatures. 8. Quadrupole Effects and Resonance. 9. Nuclear Orientation. 10. Double Resonance. 11. Beam Methods. 5. The Magnetic Properties of an Electron Gas. 1. Statistical and Thermodynamic Functions for an Electron Gas. 2. The Spin Paramagnetism of the Electron Gas. 3. The Diamagnetism of the Electron Gas. 4. Comparison of Susceptibility Theory with Experiment. 5. The De Haas--Van Alphen Effect. 6. Galvanomagnetic, Thermomagnetic, and Magnetoacoustic Effects. 7. Electron Spin Resonance in Metals. 8. Cyclotron Resonance. 9. Nuclear Magnetic Resonance in Metals. 10. Some Magnetic Properties of Superconductors. 6. Ferromagnetism. 1. Introduction. 2. The Classical Molecular Field Theory and Comparison with Experiment. The spontaneous magnetization region. The paramagnetic region. Thermal effects. 3. The Exchange Interaction. 4. The Series Expansion Method. 5. The Bethe--Peierls--Weiss Method. 6. Spin Waves. 7. Band Model Theories of Ferromagnetism. 8. Ferromagnetic Metals and Alloys. 9. Crystalline Anisotropy. 10. Magnetoelastic Effects. 7. The Magnetization of Ferromagnetic Materials. 1. Introduction. 2. Single--Domain Particles. Critical size. Hysteresis loops. Incoherent rotations. Some experimental results. Other effects. 3. Superparamagnetic Particles. 4. Permanent Magnet Materials. 5. Domain Walls. 6. Domain Structure. 7. The Analysis of the Magnetization Curves of Bulk Material. Domain wall movements. Coercive force. Initial permeability. Picture frame specimens. The approach to saturation. Remanence. Nucleation of domains: whiskers. Barkhausen effect. Preisach--type models. External stresses. Minor hysteresis loops. 8. Thermal Effects Associated with the Hysteresis Loop. 9. Soft Magnetic Materials. 10. Time Effects. 11. Thin Films. 8. Antiferromagnetism. 1. Introduction. 2. Neutron Diffraction Studies. 3. Molecular Field Theory of Antiferromagnetism. Behavior above the Neel temperature. The Neel temperature. Susceptibility below the Neel temperature. Sublattice arrangements. The paramagnetic--antiferromagnetic transition in the presence of an applied magnetic field. Thermal effects. 4. Some Experimental Results for Antiferromagnetic Compounds. 5. The Indirect Exchange Interaction. 6. More Advanced Theories of Antiferromagnetism. The series expansion method. The Bethe--Peierls--Weiss method. Spin waves. 7. Crystalline Anisotropy: Spin Flopping. 8. Metals and Alloys. 9. Canted Spin Arrangements. 10. Domains in Antiferromagnetic Materials. 11. Interfacial Exchange Anisotropy. 9. Ferrimagnetism. 1. Introduction. 2. The Molecular Field Theory of Ferrimagnetism. Paramagnetic region. The ferrimagnetic Neel temperature. Spontaneous magnetization. Extension to include additional molecular fields. Triangular and other spin arrangements. Three sublattice systems. Ferromagnetic interaction between sublattices. 3. Spinels. 4. Garnets. 5. Other Ferrimagnetic Materials. 6. Some Quantum Mechanical Results. 7. Soft Ferrimagnetic Materials. 8. Some Topics in Geophysics. 10. Resonance in Strongly Coupled Dipole Systems. 1. Introduction. 2. Magnetomechanical Effects. 3. Ferromagnetic Resonance. 4. Energy Formulation of the Equations of Motion. 5. Resonance in Ferromagnetic Metals and Alloys. 6. Ferromagnetic Resonance of Poor Conductors. 7. Magnetostatic Modes. 8. Relaxation Processes. Relaxation via spin waves in insulators. Relaxation via spin waves in conductors. Fast relaxation via paramagnetic ions. Slow relaxation via electron redistribution. 9. Nonlinear Effects. 10. Spin--Wave Spectra of Thin Films. 11. Electromagnetic Wave Propagation in Gyromagnetic Media. 12. Resonance in Unsaturated Samples. 13. Ferrimagnetic Resonance. 14. Antiferromagnetic Resonance. 15. Nuclear Magnetic Resonance in Ordered Magnetic Materials. 16. The Mossbauer Effect. Appendix I. Systems of Units. Appendix II. Demagnetization Factors for Ellipsoids of Revolution. Appendix III. Periodic Table of the Elements. Appendix IV. Numerical Values for Some Important Physical Constants. Author Index. Subject Index.
1,665 citations
TL;DR: In this article, it is shown that magnetic heat pumping can be made practical at room temperature by using a ferromagnetic material with a Curie point at or near operating temperature and an appropriate regenerative thermodynamic cycle.
Abstract: It is shown that magnetic heat pumping can be made practical at room temperature by using a ferromagnetic material with a Curie point at or near operating temperature and an appropriate regenerative thermodynamic cycle. Measurements are performed which show that gadolinium is a resonable working material and it is found that the application of a 7-T magnetic field to gadolinium at the Curie point (293 K) causes a heat release of 4 kJ/kg under isothermal conditions or a temperature rise of 14 K under adiabatic conditions. A regeneration technique can be used to lift the load of the lattice and electronic heat capacities off the magnetic system in order to span a reasonable temperature difference and to pump as much entropy per cycle as possible
833 citations
TL;DR: In this article, a reciprocating magnetic refrigerator that uses water as a heat transfer fluid has been demonstrated to achieve cooling powers exceeding 500 watts at coefficients of performance of 6 or more.
Abstract: Magnetic refrigeration has been viewed as primarily a cryogenic technology because the necessary high magnetic fields are most easily provided by superconducting magnets. However, some of the largest magnetocaloric effects are exhibited by gadolinium-based alloys near room temperature. Ames Laboratory and Astronautics Corporation of America have been collaborating to apply such materials to large-scale commercial and industrial cooling near room temperature. Astronautics has designed and operated a reciprocating magnetic refrigerator that uses water as a heat transfer fluid. The device uses the active magnetic regeneration concept of recent cryogenic devices, but in contrast to the cryogenic case, the heat capacity of the fluid in the pores of the regenerator bed is comparable to that of the solid matrix. Using a 5 T field, the refrigerator reliably produces cooling powers exceeding 500 watts at coefficients of performance of 6 or more. This record performance puts magnetic refrigeration in a class with the best of current technology, vapor cycle refrigeration, without having to use volatile, environmentally hazardous fluids.
643 citations
425 citations