Kikuchi et al. Reply: In the preceding Comment [1], Gu and Su (GS) reported the finite temperature transfer matrix renormalization group (TMRG) method results for the distorted diamond chain (DDC) model. They pointed out that the double-peak behavior of T found in experiment cannot be reproduced by our parameter set J 1 :J 2 :J 3 1:1:25:0:45 [2], but well fitted by J 1 :J 2 :J 3z 1:1:9: ÿ 0:3 with J 3x =J 3z J 3y =J 3z 1:7.In response to GS's Comment, we have performed the additional density matrix renormalization group (DMRG) and the exact diagonalization calculations for the magnetization curve MH at T 0 of the DDC model with GS's parameter set. As can be seen from Fig. 1, the DMRG MH curve with GS's parameter set does not well explain the experimental results.The positional relations between Cu 2 ions corresponding to J 1 and J 3 are very similar to each other as can be seen in the schematic view of the crystal structure of Cu 3 CO 3 2 OH 2 in Fig. (1b) of our previous Letter [2]. The distance of two Cu 2 ions corresponding to J 1 is 327.5 pm with bond angle 113.7 and that to J 3 is 329.0 pm with bond angle 113.5 . Thus it is unlikely that J 1 is antiferromagnetic without the XXZ anisotropy while J 3 is ferromagnetic with strong XXZ anisotropy. Further, as far as we know, such a strong XXZ anisotropy has not been observed at all in the S 1=2 spin systems of Cu 2 ions.The double-peak behaviors of T and CT are not necessarily attributed to the frustration effect. The mechanism for the double-peak behaviors will be as follows. In the case of J 2 J 1 , jJ 3 j as lowering the temperature, spins coupled by J 2 are going to form singlet dimers at first. The remaining spins are nearly free because they are separated PRL 97,

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We synthesized a series of CoAs based weakly itinerant ferromagnetic compound LCoAsO ͑L: lanthanoids͒ and systematically studied a L dependence on magnetic properties. Lattice constants a and c decrease monotonically with the decrease in the ion size of L 3+ . In the cases of L = Nd, Sm, and Gd, a ferromagneticantiferromagnetic transition was observed at T N = 15, 35, and 75 K, respectively, indicating the existence of unconventional interaction between ferromagnetically ordered itinerant electrons of Co. The Curie temperature T C increases from 55 to 75 K by changing La to Ce while from Ce to Gd the T C does not change so much, being quite similar to the L site dependence of the superconducting transition temperature T c in FeAs-based high-T c compound LFeAsO. We discussed the mechanism of ferromagnetic-antiferromagnetic transition and the lanthanoid dependence of T C .

The magnetic susceptibility, high field magnetization, and specific heat measurements of Cu3(CO3)2(OH)2, which is a model substance for the frustrating diamond spin chain model, have been performed using single crystals. Two broad peaks are observed at around 20 and 5 K in both magnetic susceptibility and specific heat results. The magnetization curve has a clear plateau at one third of the saturation magnetization. The experimental results are examined in terms of theoretical expectations based on exact diagonalization and density matrix renormalization group methods. An origin of magnetic anisotropy is also discussed.

We synthesized weakly itinerant ferromagnet with layered structure LaCoAsO and measured the isothermal magnetizations at various temperatures. The isothermal magnetizations in a form of Arrott plot for weakly itinerant ferromagnets such as ZrZn 2 , Sc 3 In, Ni 3 Al, and Y͑Co, Al͒ 2 shows parallel linear relation over the wide temperature range near the Curie temperature T C , while for LaCoAsO the square of the magnetization M 2 was found to show a convex curvature against H / M, similar to MnSi and Fe x Co 1−x Si. We analyzed the magnetization of LaCoAsO at T C and estimated several parameters of spin fluctuations on the basis of self-consistent renormalization theory of spin fluctuations. We simulated a reciprocal magnetic susceptibility above T C and discussed the nature of spin fluctuations in LaCoAsO.

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SiO 2 and phosphosilicate glass ͑PSG͒ films containing Si nanocrystals ͑nc-Si͒ as small as a few nanometers were studied by electron spin resonance ͑ESR͒ and photoluminescence ͑PL͒, and the correlation between the two measurements was examined. It is shown that the incorporation of nc-Si in SiO 2 results in the drastic increase in the ESR signal; the signal is assigned to the Si dangling bonds at the interfaces between nc-Si and matrices (P b centers͒. The ESR signal becomes weaker by doping P into SiO 2 matrices, i.e., by using PSG as matrices. By increasing the P concentration, the ESR signal decreases further. By decreasing the ESR signal, the low-energy PL peak at 0.9 eV decreases, while the band-edge PL at 1.4 eV increases. These results suggest that the 0.9 eV peak is related to P b centers, and that the decrease in the density of the P b centers by P doping brings about an improvement in the band-edge PL efficiency of nc-Si.

The phenomenon of spin-crossover between the low-spin (LS) and high-spin (HS) states, [1] which is observed in some octahedral 3d n (4 n 7) metal complexes and is induced by an external perturbation, such as temperature, pressure, or light irradiation, is one of the most spectacular examples of molecular bistability. [2, 3] Such phenomena can be utilized in new electronic devices, such as molecular memories and switches that are controlled by many different physical channels. [4,5] It is now established that cooperative spincrossover, the interaction between spin-crossover sites, is the predominant factor governing bistability. [6,7] We now report the first homochiral mixed-valence spin-crossover compound, in which three independent properties are united, namely, mixed valence states of iron metal centers, spin-crossover of the Fe II