Gradual Transition From Insulator To Semimetal Of Ca1-x Eux B6 With Increasing Eu Concentration

The local environment of Eu2+ (4 f7, S=7 2) in Ca1-x Eux B6 (0.003≤x≤1.00) is investigated by means of electron spin resonance (ESR). For x 0.003 the spectra show resolved fine and hyperfine structures due to the cubic crystal electric field and nuclear hyperfine field, respectively. The resonances have Lorentzian line shape, indicating an insulating environment for the Eu2+ ions. For 0.003 x 0.07, as x increases, the ESR lines broaden due to local distortions caused by the Eu Ca ions substitution. For 0.07 x 0.30, the lines broaden further and the spectra gradually change from Lorentzian to Dysonian resonances, suggesting a coexistence of both insulating and metallic environments for the Eu2+ ions. In contrast to Ca1-x Gdx B6, the fine structure is still observable up to x≈0.15. For x 0.30 the fine and hyperfine structures are no longer observed, the line width increases, and the line shape is purely Dysonian, anticipating the semimetallic character of EuB6. This broadening is attributed to a spin-flip scattering relaxation process due to the exchange interaction between conduction and Eu2+ 4f electrons. High-field ESR measurements for x 0.15 reveal smaller and anisotropic linewidths, which are attributed to magnetic polarons and Fermi surface effects, respectively. © 2005 The American Physical Society.7118Young, D.P., (1999) Nature (London), 397, p. 412. , NATUAS 0028-0836 10.1038/17081Zhitomirsky, M.E., (1999) Nature (London), 402, p. 251. , NATUAS 0028-0836 10.1038/46204Balents, L., Varma, C.M., (2000) Phys. Rev. Lett., 84, p. 1264. , PRLTAO 0031-9007 10.1103/PhysRevLett.84.1264Barzykin, V., Gor'Kov, L.P., (2000) Phys. Rev. Lett., 84, p. 2207. , PRLTAO 0031-9007 10.1103/PhysRevLett.84.2207Jarlborg, T., (2001) Physica B, 307, p. 291. , PHYBE3 0921-4526 10.1016/S0921-4526(01)00629-9Jarlborg, T., (2000) Phys. Rev. Lett., 85, p. 186. , PRLTAO 0031-9007 10.1103/PhysRevLett.85.186Ceperley, D., (1999) Nature (London), 397, p. 386. , NATUAS 0028-0836 10.1038/17011Tromp, H.J., (2001) Phys. Rev. Lett., 87, p. 016401. , PRLTAO 0031-9007 10.1103/PhysRevLett.87.016401Massidda, S., Continenza, A., De Pascale, T.M., Monnier, R., (1997) Z. Phys. B: Condens. Matter, 102, p. 83. , ZPCMDN 0722-3277 10.1007/s002570050267Urbano, R.R., Rettori, C., Barberis, G.E., Torelli, M., Bianchi, A., Fisk, Z., Pagliuso, P.G., Oseroff, S.B., (2002) Phys. Rev. B, 65, p. 180407. , PRBMDO 0163-1829 10.1103/PhysRevB.65.180407Moriwaka, T., (2001) J. Phys. Soc. Jpn., 70, p. 341. , JUPSAU 0031-9015 10.1143/JPSJ.70.341Hall, D., (2001) Phys. Rev. B, 64, p. 233105. , PRBMDO 0163-1829 10.1103/PhysRevB.64.233105Vonlanthen, P., (2000) Phys. Rev. B, 62, p. 10076. , PRBMDO 0163-1829 10.1103/PhysRevB.62.10076Ott, H.R., (1997) Z. Phys. B: Condens. Matter, 102, p. 337. , ZPCMDN 0722-3277 10.1007/s002570050297Gavilano, J.L., (2001) Phys. Rev. B, 63, p. 140410. , PRBMDO 0163-1829 10.1103/PhysRevB.63.140410Gianniò, K., (2002) J. Phys.: Condens. Matter, 14, p. 1035. , JCOMEL. 0953-8984. 10.1088/0953-8984/14/5/308Denlinger, J.D., (2002) Phys. Rev. Lett., 89, p. 157601. , PRLTAO 0031-9007 10.1103/PhysRevLett.89.157601Rhyee, J., Cho, B.K., Ri, H.-C., (2003) Phys. Rev. B, 67, p. 125102. , PRBMDO 0163-1829 10.1103/PhysRevB.67.125102Souma, S., Komatsu, H., Takahashi, T., Kaji, R., Sasaki, T., Yokoo, Y., Akimitsu, J., (2003) Phys. Rev. Lett., 90, p. 027202. , PRLTAO 0031-9007 10.1103/PhysRevLett.90.027202Terashima, T., (2000) J. Phys. Soc. Jpn., 69, p. 2423. , JUPSAU 0031-9015 10.1143/JPSJ.69.2423Matsubayashi, K., (2002) Nature (London), 420, p. 143. , NATUAS 0028-0836 10.1038/420143bFisk, Z., (2002) Nature (London), 420, p. 144. , NATUAS 0028-0836 10.1038/420144aBennett, M.C., Van Lierop, J., Berkeley, E.M., Mansfield, J.F., Henderson, C., Aronson, M.C., Young, D.P., Lacerda, A., (2004) Phys. Rev. B, 69, p. 132407. , PRBMDO 0163-1829 10.1103/PhysRevB.69.132407Süllow, S., (1998) Phys. Rev. B, 57, p. 5860. , PRBMDO. 0163-1829. 10.1103/PhysRevB.57.5860Paschen, S., (2000) Phys. Rev. B, 61, p. 4174. , PRBMDO 0163-1829 10.1103/PhysRevB.61.4174Wigger, G.A., Walti, Ch., Ott, H.R., Bianchi, A.D., Fisk, Z., (2002) Phys. Rev. B, 66, p. 212410. , PRBMDO 0163-1829 10.1103/PhysRevB.66.212410Wigger, G.A., Monnier, R., Ott, H.R., Young, D.P., Fisk, Z., (2004) Phys. Rev. B, 69, p. 125118. , PRBMDO 0163-1829 10.1103/PhysRevB.69.125118Calderon, M.J., Wegener, L.G.L., Littlewood, P.B., (2004) Phys. Rev. B, 70, p. 092408. , PRBMDO 0163-1829 10.1103/PhysRevB.70.092408Kuneš, J., Pickett, W.E., (2004) Phys. Rev. B, 69, p. 165111. , PRBMDO 0163-1829 10.1103/PhysRevB.69.165111Pereira, V.M., Lopes Dos Santos, J.M.B., Castro, E.V., Castro-Neto, A.H., (2004) Phys. Rev. Lett., 93, p. 147202. , PRLTAO 0031-9007 10.1103/PhysRevLett.93.147202Urbano, R.R., Pagliuso, P.G., Sarrao, J.L., Oseroff, S.B., Rettori, C., Bianchi, A., Nakatsuji, S., Fisk, Z., (2004) J. Magn. Magn. Mater., 272-276 (1 SUPPL.), p. 1659. , JMMMDC 0304-8853Urbano, R.R., Pagliuso, P.G., Rettori, C., Oseroff, S.B., Sarrao, J.L., Schlottmann, P., Fisk, Z., (2004) Phys. Rev. B, 70, p. 140401. , PRBMDO 0163-1829 10.1103/PhysRevB.70.140401Abragam, A., Bleaney, B., (1970) EPR of Transition Ions, , Clarendon Press, OxfordDavidov, D., Rettori, C., Zevin, V., (1975) Solid State Commun., 16, p. 247. , SSCOA4 0038-1098 10.1016/0038-1098(75)90584-0Rettori, C., Davidov, D., Grayewskey, A., Walsh, W.M., (1975) Phys. Rev. B, 11, p. 4450. , PLRBAQ 0556-2805 10.1103/PhysRevB.11.4450Luft, H., Baberschke, K., Winzer, K., (1982) Z. Phys. B: Condens. Matter, 47, p. 195. , ZPCMDN 0722-3277Oseroff, S.B., Calvo, R., (1978) Phys. Rev. B, 18, p. 3041. , PLRBAQ 0556-2805 10.1103/PhysRevB.18.3041Pake, G.E., Purcell, E.M., (1948) Phys. Rev., 74, p. 1184. , PHRVAO 0031-899X 10.1103/PhysRev.74.1184Bloembergen, N., (1952) J. Appl. Phys., 23, p. 1383. , JAPIAU 0021-8979 10.1063/1.1702079Feher, G., Kip, A.F., (1955) Phys. Rev., 98, p. 337. , PHRVAO 0031-899X 10.1103/PhysRev.98.337Dyson, F.J., (1955) Phys. Rev., 98, p. 349. , PHRVAO 0031-899X 10.1103/PhysRev.98.349Sperlich, G., Jansen, K., (1974) Solid State Commun., 15, p. 1105. , SSCOA4 0038-1098 10.1016/0038-1098(74)90542-0Buckmaster, H.A., Shing, Y.H., (1972) Phys. Status Solidi a, 12, p. 325. , PSSABA 0031-8965Bartkowski, M., Northcott, D.J., Park, J.M., Deddoch, A.H., Hedgcock, F.T., (1985) Solid State Commun., 56, p. 659. , SSCOA4 0038-1098 10.1016/0038-1098(85)90773-2Davidov, D., Maki, K., Orbach, R., Rettori, C., Chock, E.P., (1973) Solid State Commun., 12, p. 621. , SSCOA4 0038-1098 10.1016/0038-1098(73)90299-8Essam, J.W., (1972) Phase Transitions and Critical Phenomena, 2, p. 197. , edited by C. Domb and M. S. Green (Academic Press, LondonSchlottmann, P., Hellberg, C.S., (1996) J. Appl. Phys., 79, p. 6414. , JAPIAU 0021-8979 10.1063/1.362014Oseroff, S., Calvo, R., Stankiewicz, J., Fisk, Z., Johnston, D.C., (1979) Phys. Status Solidi B, 94, p. 133. , PSSBBD 0370-1972Aronson, M.C., Sarrao, J.L., Fisk, Z., Whitton, M., Brandt, B.L., (1999) Phys. Rev. B, 59, p. 4720. , PRBMDO 0163-1829 10.1103/PhysRevB.59.4720Fisk, Z., (1979) J. Appl. Phys., 50, p. 1911. , JAPIAU 0021-8979 10.1063/1.327162Goodrich, R.G., Harrison, N., Vuillemin, J.J., Teklu, A., Hall, D.W., Fisk, Z., Young, D., Sarrao, J., (1998) Phys. Rev. B, 58, p. 14896. , PRBMDO 0163-1829 10.1103/PhysRevB.58.14896Götze, W., Wölfle, P., (1971) J. Low Temp. Phys., 5, p. 575. , JLTPAC. 0022-2291Wigger, G.A., Beeli, C., Felder, E., Ott, H.R., Bianchi, A.D., Fisk, Z., (2004) Phys. Rev. Lett., 93, p. 147203. , PRLTAO 0031-9007 10.1103/PhysRevLett.93.14720