Magnetocaloric Materials

Abstract

Key Words magnetocaloric effect, mixed lanthanide materials, 3d-materials amorphous alloys, manganites s Abstract In the last decade of the twentieth century there has been a significant increase in research on a more than 100-year old phenomenon-the magnetocaloric effect (MCE). As a result, many new materials with large MCEs (and many with lesser values) have been discovered, and a much better understanding of this magneto-thermal property has resulted. In this review we briefly discuss the principles of magnetic cooling (and heating); the measurement of the magnetocaloric properties by direct and indirect techniques; the special problems that can arise; and the MCE properties of the 4f lanthanide metals, their intra-lanthanide alloys and their compounds [including the giant MCE Gd 5 (Si x Ge 1−x ) 4 phases]; the 3d transition metals, their alloys and compounds; and mixed lanthanide-3d transition metal materials (including the La manganites). INTRODUCTIONCommercial and residential refrigeration is a mature, relatively low capital cost but a high-energy demand industry. Even the newest most efficient units operate well below the maximum theoretical (Carnot) efficiency, and few, if any, further improvements may be possible with the existing vapor-cycle technology. Magnetic refrigeration (MR), however, is rapidly becoming competitive with conventional gas compression technology because it offers considerable operating cost savings by eliminating the most inefficient part of the refrigerator-the compressor. In addition to its energy savings potential, MR is an environmentally sound alternative to vapor-cycle refrigerators and air conditioners. Most modern refrigeration systems and air conditioners still use ozone-depleting or global-warming volatile liquid refrigerants. Magnetic refrigerators use a solid refrigerant(s) and common heat transfer fluids (e.g. water, water-alcohol solution, air, or helium gas) with no ozone-depleting and/or global-warming effects.Magnetic refrigeration is based on the magnetocaloric effect (MCE). The MCE, or adiabatic temperature change ( T ad ), which is detected as the heating or the cooling of magnetic materials due to a varying magnetic field, was originally discovered in iron by Warburg (1). The thermodynamics of the MCE was understood 0084-6600/00/0801-0387$14.00 387 Annu. Rev. Mater. Sci. 2000.30:387-429. Downloaded from www.annualreviews.org by Fordham University on 11/22/12. For personal use only. 388GSCHNEIDNER PECHARSKY by Debye (2) and by Giauque (3), both of whom independently suggested that it could be used to reach low temperatures in a process known as adiabatic demagnetization. Soon after this discovery, an operating adiabatic demagnetization refrigerator was constructed and utilized by Giauque & McDougal (4) to reach 0.53, 0.34, and 0.25 K starting at 3.4, 2.0, and 1.5 K, respectively, using a magnetic field of 0.8 T and 61 g of Gd 2 (SO 4 ) 3 ·8H 2 O as the magnetic refrigerant. The MCE is intrinsic to any magnetic material. In the case of a ferromagnet near its mag...

Fe doping effects on the structural, magnetic, and magnetocaloric properties of nano-sized Pr0.6Bi0.4Mn1−x Fe x O3 (0.1 ≤ x ≤ 0.3) manganites

“…Since the discovery of the magnetocaloric effect (MCE) in the pure Gadolinium, numerous materials have been the subject of intensive study in order to improve their magnetocaloric properties and to propose them as potential candidate materials for magnetic refrigeration [1,2]. Owing to their substantial MCE, the perovskite manganites with the general formula Ln 1-x A x MnO 3 , where Ln is a rare earth ion (Ln = La, Pr, Sm …) and A is a divalent element (A = Ca, Sr, Ba …), have attracted great interest for their colossal magnetoresistance (CMR) and MCE [3][4][5][6].…”

“…In fact, magnetic refrigeration is becoming a promising technology to replace the conventional gas compression-expansion technique. For sub-room temperature magnetic refrigeration applications, gadolinium is the first material known to show a large MCE, since it exhibits a maximum value of magnetic entropy change, DS max M , of 5 J/kg K at 294 K under an applied magnetic field of 2 T [1]. As it is well known, their essential magnetic properties are explained by the double exchange (DE) interaction between Mn 3?…”

Structural and Magnetic Studies of the Fe-Co-Zr-Mo-W-B Amorphous Alloy

“…The MCE offers an energy efficient and environmental friendly alternative to the traditional refrigeration or heat pumps [1][2][3]. The development of Fe-based amorphous soft magnetic materials with a wide supercooled liquid region and good glass formability has become an important research topic in recent years [4][5][6].…”

Evaluation of the reliability of the measurement of key magnetocaloric properties: A round robin study of La(Fe,Si,Mn)Hδ conducted by the SSEEC consortium of European laboratories

“…It is known as the giant magnetocaloric effect (GMCE) when a first order coupled magneto-structural or magneto-elastic transformation takes place. Indeed, the discovery of GMCE in Gd 5 (Si 2 Ge 2 ) , initiated intense research activity (Gschneidner and Pecharsky 2000;Tegus et al 2002) and the MCE has received growing interest more widely due to its potential use for environmentally friendly and energy efficient solid state magnetic cooling at room temperature (Gschneidner 2005Sandeman 2011;Tassou et al 2010). …”