Gallium Garnet Gd3Ga5O12 Research Articles

Growth and microwave properties of layered ferrogarnet structures

The ferrogarnet structures consisting from one- to three- layers of monocrystalline yttrium-iron garnet Y3Fe5O12 (YIG) films, two- layered YIG - La,Ga:YIG and two- layered {Y,Sm,Lu}3(Fe,Ga)5O12 -YIG structures were grown by liquid-phase epitaxy (LPE) method on gadolinium - gallium garnet Gd3Ga5O12 (GGG) substrates of (111) orientation. The obtained layered ferrogarnet structures were studied by the methods of ferromagnetic resonance (FMR) and magnetostatic wave (MSW) interference. The two- and three- layered YIG structures have a wide FMR line width (∆H). For the three- layered YIG structures with the total thickness of 68-102 μm ∆H = 5,7- 11,5 Oe. The line width ∆H = 0,34 – 1,22 Oe correspond to the two- layered (Y,Sm,La)3(Fe,Ga)5O12 – YIG structures with thicknesses from 3 to 65 μm. Individual layers in all structures are characterized by similar or different saturation magnetizations (4πMs).The frequency MSW separation in the YIG - La,Ga:YIG layered structure was observed. It was shown that the propagation losses of MSW in one- and two- layered structures increase with decreasing wavelength of MSW and transition to a two- layered structure.

Spin wave excitation in sub-micrometer thick Y3Fe5O12 films fabricated by pulsed laser deposition on garnet and silicon substrates: A comparative study

The development of yttrium iron garnet nanostructures on a silicon substrate is critically important for the integration of magnonic components with conventional electronic circuits. In this work, we present experimental data on spin wave excitation and propagation in 700 nm thick planar Y3Fe5O12 (YIG) films fabricated on gadolinium gallium garnet Gd3Ga5O12 (GGG) and silicon substrates by pulsed laser deposition. The spin wave spectroscopy measurements were accomplished using a set of micro-antennas placed directly on the film surface. The data were collected in a frequency range of 0.5–7 GHz and a bias magnetic field from 0 to 2000 Oe. We compare and analyze the spectra obtained for YIG/GGG and YIG/Si. Fitting to the Kittel formula yields the effective magnetization of the samples which is compared with the results obtained by magnetometry. Application of spin wave spectroscopy for magnetic film characterization allows us to extract valuable information on the magnetic texture. Understanding the mechanisms leading to the spin wave damping modification is the key to low-loss spin wave devices compatible with conventional silicon-based technology.

5 7 Fe Emission Mössbauer Study on Gd 3 Ga 5 O 1 2 implanted with dilute 5 7 Mn

57Fe emission Mossbauer spectroscopy has been applied to study the lattice location and properties of Fe in gadolinium gallium garnet Gd3Ga5 O 12 (GGG) single crystals in the temperature interval 300 – 563 K within the extremely dilute (<10−4 at.%) regime following the implantation of57Mn (T 1 / 2= 1.5 min.) at ISOLDE/CERN. These results are compared with earlier Mossbauer spectroscopy study of Fe-doped gadolinium gallium garnet Gd3Ga5 O 12(GGG), with implantation fluences between 8×1015 and 6×1016 atoms cm−2. Three Fe components are observed in the emission Mossbauer spectra: (i) high spin Fe2+ located at damage sites due to the implantation process, (ii) high spin Fe3+ at substitutional tetrahedral Ga sites, and (iii) interstitial Fe, probably due to the recoil imparted on the daughter57∗Fe nucleus in the β − decay of57Mn. In contrast to high fluence57Fe implantation studies the Fe3+ ions are found to prefer the tetrahedral Ga site over the octahedral Ga site. No annealing stages are evident in the temperature range investigated. Despite the very low concentration, high-spin Fe3+ shows fast spin relaxation, presumably due to an indirect interaction between nearby gadolinium atoms.

Static contribution to thermal shifts of spectral lines in gadolinium gallium garnet Gd3Ga5O12:Nd3+ laser crystal

The static contribution due to lattice thermal expansion and the vibrational contribution due to electron–phonon interaction to the thermal shifts of the spectral lines E1(R1 → Z5) and E2 (R2 → Z5) in the high-power laser crystal gadolinium gallium garnet Gd3Ga5O12 (GGG):Nd3+ are studied by analyzing the observed pressure- and temperature-dependence of these spectral lines. It is found that the static contribution due to thermal expansion in magnitude is greater than, and it in sign is opposite to the vibrational contribution due to electron–phonon interaction. So for the theoretical study of thermal shifts of the spectral lines in GGG:Nd3+ and other similar “hard” crystals, the neglect of the contribution due to the lattice thermal expansion suggested in the previous papers is unsuitable.

Experimental investigation of the quantum amplification effect for magnetostatic waves in ferrite-paramagnet structures

The effect of quantum amplification of the forward bulk magnetostatic waves (MSWs) in a composite structure of yttrium iron garnet Y3Fe5O12 (YIG) and Al2O3:Cr3+ (ruby) was studied. The maximum amplification coefficient at 4.2 and 1.6 K was 12 and 25 dB, respectively. No MSW amplification was observed in an epitaxial structure comprising an YIG film grown on a gadolinium gallium garnet Gd3Ga5O12 (GGG) substrate, which is explained by a strong paramagnetic absorption of MSWs in the GGG substrate crystal.

Analog to the 4He melting curve in a model geometrically frustrated magnet

Gadolinium gallium garnet, Gd3Ga5O12 (GGG) has an extraordinary low-temperature phase diagram. Although the Curie–Weiss temperature of GGG is ~–2 K, GGG shows no long-range order down to T ~ 0.4 K. At low temperatures GGG has a spin-glass phase at low fields ([Formula: see text] 0.08 T), a field-induced long-range-ordered anti-ferromagnetic (AFM) phase at fields of between 0.7 and 1.3 T, and, at intermediate fields, an apparent spin-liquid (SL) phase without long-range order. We have performed specific heat, magnetocaloric, and static magnetization measurements near the SL/AFM phase boundary. Our results show that the lower field boundary of the AFM phase has a distinct minimum at T ~ 0.2 K, in analogy to the minimum in the melting curve of 4He. PACS Nos.: 75.30Kz, 75.50Ee

Study of the low temperature thermal properties of the geometrically frustrated magnet: Gadolinium gallium garnet

Gadolinium gallium garnet, Gd3Ga5O12 (GGG) has an extraordinary low temperature phase diagram. Although the Curie–Weiss temperature of GGG is about −2 K, GGG shows no long-range order down to T∼0.4 K. At low temperatures GGG has a spin glass phase at low fields (⩽0.1 T) and a field-induced long-range order antiferromagnetic state at fields of between 0.7 and 1.3 T [P. Schiffer et al., Phys. Rev. Lett. 73, 2500 (1994), S. Hov, H. Bratsberg, and A. T. Skjeltorp, J. Magn. Magn. Mater. 15–18, 455 (1980); S. Hov, Ph.D. thesis, University of Oslo, 1979 (unpublished), A. P. Ramirez and R. N. Kleiman, J. Appl. Phys. 69, 5252 (1991)]. However, the nature of the ground state at intermediate fields is still unknown, and has been hypothesized to be a three-dimensional spin liquid. We have measured the thermal conductivity (κ) and heat capacity (C) of a high-quality single crystal of GGG in the low temperature regime in order to study the nature of this state. The field dependence of κ shows that phonons are the predominant heat carriers and are scattered by spin fluctuations. We observe indications in κ(H) and C(H) of both the field induced ordering and the spin glass phase at low temperatures (T⩽200 mK).