86 magnetic properties of the spatially segregated constituent manganese-oxide phases b-MnO2 and a-Mn2O3, whereas the FM component is most likely associated with the not-well-understood magnetism of the mismatch layer at the interface between these two phases. The interior b-MnO2 phase and the a-Mn2O3 thin surface layer both exhibit AFM properties anal- ogous to their bulk phases (the temperatures of the maxima in the T-dependent magnetization of the nanorods and the bulk materials match well) despite the nanodimensions of the rods. These results show how important it is to make a thorough structural characterization of the material on the atomic-resolu- tion scale before entering the discussion on the inﬂuence of nanodimensions on the physical properties of the material. We should also like to mention that similar structure of a thin surface layer of another phase that covers the basic b-MnO2 material was observed (see Fig. 3d of [7]), though not discussed, also for the b-MnO2 nanorods produced by the selected- control hydrothermal synthesis [7], so that this kind of structure of the b-MnO2 nanorods seems to appear quite commonly. Conclusions To summarize, we presented a hydrothermal method for the synthesis of structurally well-ordered single- crystalline b-MnO2 nanorods. We show that the basic b-MnO2 material is covered by a thin surface layer of the a-Mn2O3 phase with a reduced Mn valence that adds its own magnetic signal to the total magnetization. The nanodimensions of the investigated nanorods do not appear to affect signiﬁcantly their magnetic response, which can be explained as a superposition of bulk magnetic properties of the spatially segregated constituent manganese-oxide phases and the magne- tism of the thin interface between them. This result Nanoscale Res Lett (2007) 2:81–86 prompts for further investigations of the magnetism of nano-sized materials in order to prove/disprove the often-claimed exceptionality of magnetism on the nanometric scale. Acknowledgment This work was supported by the Frontier Research Laboratory Program at the Korea Basic Science Institute. References 1. C. Dekker, Phys. Today 52, 22 (1999) 2. X. Duan, Y. Huang, Y. Cui, J. Wang, C.M. Lieber, Nature 409, 66 (2001) 3. Y. Xia, P. Yang, Y. Sun, Y. Wu, B. Mayers, B. Gates, Y. Yin, F. Kim, H. Yan, Adv. Mater. 15, 353 (2003) 4. C.N.R. Rao, F.L. Deepak, G. Gundiah, A. Govindaraj, Prog. Solid Chem. 31, 5 (2003) 5. M.M. Thackeray, Prog. Solid State Chem. 25, 1 (1997) 6. X. Chen, X. Li, Y. Jiang, C. Shi, X. Li, Solid State Commun. 136, 94 (2005) 7. X. Wang, Y. Li, J. Am. Chem. Soc. 124, 2880 (2002) 8. C.W. Na, D.S. Han, D.S. Kim, J. Park, Y.T. Jeon, G. Lee, M.-H. Jung, Appl. Phys. Lett. 87, 142504 (2005) 9. W. Liu, G.C. Farrington, F. Chaput, B. Dunn, J. Electro- chem. Soc. 143, 879 (1996) 10. M. Matzapetakis, N. Karligiano, A. Bino, M. Dakanali, C.P. Raptopoulou, V. Tangoulis, A. Terzis, J. Giapintzakis, A. Salifoglou, Inorg. Chem., 39, 4044 (2000) 11. M. Regulski, R. Przeniosło, I. Sosnowska, J.-U. Hoffmann, J. Phys. Soc. Japan 73, 3444 (2004) 12. N. Ohama, Y. Hamaguchi, J. Phys. Soc. Japan 30, 1311 (1971) 13. M. Regulski, R. Przeniosło, I. Sosnowska, D. Hohlwein, R. Schneider, J. Alloys Compd. 362, 236 (2004) 14. E.G. King, J. Am. Chem. Soc. 76, 3289 (1954) 15. R.W. Grant, S. Geller, J.A. Cape, G.P. Espinoza, Phys. Rev. 175, 686 (1968) 16. S.H. Kim, B.J. Choi, G.H. Lee, S.J. Oh, B. Kim, H.C. Choi, J. Park, Y. Chang, J. Korean Phys. Soc. 46, 941 (2005) 17. B. Boucher, R. Buhl, M. Perrin, J. Appl. Phys. 42, 1615 (1971) 18. W.S. Seo, H.H. Jo, K. Lee, B. Kim, S.J. Oh, J.T. Park, Angew. Chem. 43, 1115 (2004) 19. I. S. Jacobs, Chem. Solids 11, 1 (1959)