Recent Progress on Rare Earth Magnetic Regenerator Materials

Abstract

Our group has reported several candidates for magnetic regenerator materials in the helium temperature range, such as, (Erl-xDYx)Ni2• Er(Nil-xCox)2• ErNi and Er3Ni. However, those Curie temperatures Tc's are more than ~s.s K and the specific heats C(T)'s of those systems become very small near 4.2 K. In the present investigation we have succeeded in developing a new low Tc material, Ero.gYbo.1Ni2 whose Tc is ~4 K. Moreover, other new regenerator materials, such as Erl-xYbxNi and Er1-xHoxNi2 have also been investigated and usefulness of those compounds was verified. We have also studied the origin of the small C(T) of some Er compounds near 4.2 K and it has been made clear that the Schottky type specific heat reduces the absolute value of C(T) in low temperature range.

Numerical Simulation of Magnetic Field Effect on Cryocooler Regenerators: Temperature Distribution

“…The text by Spichkin and Tishin [10] also vastly covers such materials along with their magnetic properties. As seen from [3][4][5][6][7][8][9][10] the most prominent materials used are Er 3 Ni, ErNi, HoCu 2 , and ErPr.…”

“…The use of magnetic intermetallic compounds in regenerators of cryocoolers improved its functioning below 10 K [3,4] and liquid He temperatures were reached [5,6]. The heat capacity of Pb decreases drastically whereas peak in specific heat is observed in such materials below 10 K [7][8][9].…”

Centrifugal atomization of lanthanide materials for cryogenic coolers

“…As was mentioned above, lattice vibration and conduction electrons contribute to the heat capacity of most solids. In some materials, Schottl_ anomaliesl4 and magnetic ordering l2, 14 also contribute to heat capacity. It has been found that, upon cooling, most lanthanide metals and lanthanide intermetallic compounds magnetically order at a critical temperature, either the Curie temperature, Tc, for paramagnetic ---> ferrimagnefic (or ferromagnetic) ordering, or the Ntel temperature, Tn, for paramagnetic --->antiferromagnefic ordering.12 When ordering occurs in these materials, there is a change in entropy (AS = Sj) associated with the alignment of magnetic spins in the material.…”

Hydrogen induced structural and magnetic transformations in magnetic regenerator materials ErNin (n=1, 2) and HoCu2

“…HoCu 2 and Er-Ni compounds with magnetic transition temperatures between 40 and 6 K have been applied to the magnetic regenerator materials [1][2][3][4][5]. But in order to increase the refrigeration capacity at 4.2 K, it is necessary to search for new magnetic regenerator materials with magnetic transition temperature about 4.2 K.…”

“…Magnetic compounds with the magnetic transition below 20 K may be used as magnetic regenerator materials in helium-regenerative cycle refrigerators if the magnetic compounds exhibit extremely large heat capacity in the vicinity of their magnetic transitions [1][2][3][4][5]. HoCu 2 and Er-Ni compounds with magnetic transition temperatures between 40 and 6 K have been applied to the magnetic regenerator materials [1][2][3][4][5].…”