Appl. Phys. A 61, 415-418 (1995) Applied Materials Physics A 9 Springer-Verlag 1995 Magnetization measurements on some rare-earth iron garnets M.S. Lataifeh, A. Al-sharif Department of Physics, Mu'tah University, P.O. Box 7, Mu'tah, Karak, Jordan (Fax: + 962-2/654061) Received: 25 April 1994/Accepted: 23 February 1995 Abstract. The magnetic properties of Fe-based single- crystal garnets have been studied. A magnetic field up to 55 kOe in the temperature range from 4.5 to 300 K has been used. The compensation temperature (Tcomv) of the studied garnets has been determined. The compensation temperature increases with the increase of the rare-earth ions (Ho a+ or Gd 3 § substituting y3 § ions in the c sublat- tice of R3FesO~z. Above Tcomp, the magnetization was found to be linearly field dependent. The results are in good agreement with magnetization measurements per- formed on polycrystalline samples, and with calculations based on the crystal field: parameters of the isostructural Holmium Gallium Garnet (HoGG). PACS: 75.60 The physical properties of rare-earth iron garnets have been extensively studied using different techniques [1-3]. The low temperature magnetic properties are not yet completely studied. The Rare-earth Iron Garnets (RIG) have the general unit formula R3FesO~2, where R is either a trivalent rare-earth ion or yttrium. RIGs belong to the space group Ia3d. The magnetic ions are distributed over three crystallographic si~tes,with sublattice magnetization Ma (octahedral site, 16 Fe 3§ ions in a), Md (tetrahedral site, 24 Fe 3 + ions in d), and Mc (dodecahedral site 24 R 3 + ions in c). The garnets have eight formula units in the cubic unit cell, as shown in' the'general formula. The cubic unit cell of RIGs have approximately the same lattice constant which is of the order of 12 A [4], due to similar ionic radii of R ~§ ions~ The interaction between the Fe 3 + ions in {a} and {d} sites is strongly antiferromagnetic due to, strong superexchange interaction. The magnetic mo- ment of the rare-earth ions in the ~c} sublattice couples antiparallel with the resultan~ moment of Fe 3 + ions. For all: rare-earth iron garnets, the Curie temperature is nearly the same, and i~tis.associated with paired Fe 3 + sublattices. The presence of a rare-earth sublattice has a secondary effect. In this paper, magnetization measurements in a con- tinuous magnetic field applied to certain specified crystal- lographic directions will be presented for the Holmium- Iron Garnet (HoIG). Holmium substituted yttrium in iron garnets with different concentrations (Hoo.olYo.99)3 Fe5012 and (Hol.sY1.5)F%O12, and in the Gadolinium- Iron Garnet (GdIG) with 1% holmium, (Hoo.ol Gdo.99)3 Fe5012. The magnetization measurements have been in- terpreted by using the N6el theory of ferrimagnetism. The compensation temperature as a function of rare-earth content has been measured for four different doping con- centrations. The y3 + in YIG has no magnetic moment, so the net magnetic moment in YIG is due to the unequal distribu- tion of Fe a + ions in the two different sublattices {a} and {d}. The Gd 3 § ion in GdlG is an S-state ion, (S = 7/2, L = 0), the magnetic moment per ion is 7pB. The Gd 3 § ions are magnetized parallel to the Fe 3§ ion in the a sublattice. In HoIG (Ho3F%O12), where the No 3+ ion is a non- S-state ion, the crystalline electric field causes quenching of the orbital angular momentum L. The exchange field plus the crystal electric field will cause the holmium mo- ments to have double conical arrangement relative to the easy direction of the magnetization, which is the Jill]- direction for the systems studied [5, 6]. Diluting pure HoIG with yttrium will cause the reduction of the ex- change interaction and the magnetic dipole-dipole inter- action. For Gd 3 § ions substituting Ho 3 § ions in the {c} sublattice, dilution with gadolinium will make the system more isotropic, and because the gadolinium magnetic moment follows the applied field, it is easier to rotate the other anisotropic ions such as holmium towards the hard direction of magnetization. The single-crystal garnets were supplied by the Crystal Growth Group, Clarendon Laboratory, Oxford Univer- sity. Experiments were performed by using the Super- conducting Quantum Interference Device (SQUID) magnetometer, in the temperature range from 4.5 to 300 K.