Magnetic properties of Ho@C82 and Gd@C82 were characterized in the temperature range of 1.8−100 K with an applied magnetic field up to 5 T. The isothermal magnetization curves of Gd@C82 and Ho@C82 follow the Brillouin function down to 8 and 12 K, respectively. Unlike Gd@C82, the fitting to the Curie−Wiess law for Ho@C82 results in an effective magnetic moment which is significantly smaller than that of a free Ho3+ ion. The magnetic moment reduction and the imperfect paramagnetic behavior of Ho@C82 are ascribed to the carbon cage crystal field effect, the partial hybridization of the orbitals of the entrapped Ho atom and the carbon cage, and the interactions between the metal centers.

A large magnetic entropy change has been observed in an intermetallic compound LaFe10.6Si2.4. The maximum −ΔSM≈3.2 J/kg K was found at its Curie temperature, ∼242 K, upon a 2 T magnetic field change. Although the entropy change is slightly smaller than that of pure Gd metal, such Fe-rich compounds still appear to be very attractive candidates since (a) the raw materials are much cheaper than pure Gd metal; (b) the Curie temperature can be easily shifted by tuning the composition; (c) the materials are much more chemically stable than pure Gd metal.

Apart from the scientific interest, texture development in copper thin films is of crucial importance to their applications as interconnects or corrosion resistant coating. We report here a dominant ͗110͘ texture of copper thin films-preferred for oxidation-resistant applications-deposited by direct current magnetron sputtering. Scanning electron microscopy shows that the copper films go through a transition from ͗111͘ columns to ͗110͘ hillocks as the deposition proceeds. Cross-sectional transmission electron microscopy ͑TEM͒ indicates that the ͗110͘ grains nucleate at boundaries of ͗111͘ grains. Further, we have proposed a stress-driven nucleation and growth model of ͗110͘ grains based on the x-ray diffraction characterization and the TEM observations. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1466518͔As the dimension of integrated circuits continues to shrink, it is becoming ever more crucial to control the microstructure-in particular, the texture-of metal thin films as interconnects. Tremendous amounts of effort has been devoted to texture optimization of aluminum interconnects. [1][2][3] With increasing use of copper in place of aluminum as interconnects, development of the ͗111͘ texture in copper has been a focus in recent investigations. 4 -6 On the other hand, development of the ͗110͘ texture is also preferred in oxidation-resistant applications. 7,8 As a result, numerous investigations have focused on these two textures, ͗111͘ and ͗110͘, in copper thin films.These two textures, ͗111͘ and ͗110͘, have been observed in copper films deposited by electroplating, 9,10 cathodic vacuum arcing, 11 and dry etching. 12 The magnetron sputtering deposition-an economic approach in manufacturinghas been found to produce copper films of only weak ͗110͘ texture. 13 For face-center-cubic metals, it has been demonstrated 11,14 that incident energetic particles favor the development of ͗110͘ over the ͗111͘ texture, due to the easier channeling, and thereby less localized radiation damage in the ͗110͘ grains. When the energy of incident particles is in the range of tens of electron volts, channeling effects are absent, and the heat deposition from the kinetic energy favors the thermodynamically preferred ͗111͘ texture.Apart from the damage effects, it is known that stress may be produced in thin films by energetic particles. 11,15 Further, annealing experiments show that stress may favor the ͗110͘ texture in copper films. 16 Under stress and at high temperature, hillocks of ͗110͘ texture grow at the expense of grains of ͗111͘ texture. 17,18 It is scientifically interesting and technologically important to investigate whether the ͗110͘ hillocks are also formed during deposition.In this letter, we report the development of a strong ͗110͘ texture in copper thin films, during direct current ͑dc͒ magnetron sputtering deposition. The experimental conditions are briefly summarized as follows. The sputtering power is variable from 50 to 200 W, and the chamber is filled with 99.999% Ar, flowing into the chamber at a rat...