Short-range ferromagnetism and spin-glass state inY0.7Ca0.3MnO

Abstract

Dynamic magnetic properties of Y 0.7 Ca 0.3 MnO 3 are reported. The system appears to attain local ferromagnetic order at T SRF Ϸ70 K, where SRF is short-range ferromagnetism. Below this temperature the low-field magnetization becomes history dependent, i.e., the zero-field-cooled ͑ZFC͒ and field-cooled magnetization deviate from each other and close logarithmic relaxation appears at our experimental time scales (0.3-10 4 sec). The zero-field-cooled magnetization has a maximum at T f Ϸ30 K, whereas the field-cooled magnetization continues to increase, although less sharply, also below this temperature. Surprisingly, the dynamics of the system show nonequilibrium spin-glass features not only below the maximum in the ZFC magnetization, but also in the temperature region between this maximum and T SRF . The aging and temperature cycling experiments show only quantitative differences in the dynamic behavior above and below the maximum in the ZFC magnetization; similarly, memory effects are observed in both temperature regions. We attribute the high-temperature behavior to the existence of clusters of short-range ferromagnetic order below T SRF ; the configuration evolves into a conventional spin-glass state at temperatures below T f .

Magnetic and magnetotransport properties of the orthorhombic perovskites(Lu,Ca)MnO3

“…In other words, with decreasing size of the R constituent the FM state gradually gets disfavored. The observed magnetic and transport characteristics of the present ͑Lu, Ca͒MnO 3 system resemble those of R =Y, [15][16][17][18] such that within the Casubstitution range of 0.1Յ x Յ 0.6 the ͑Lu 1−x Ca x ͒MnO 3 samples seem to be SG insulators with freezing temperatures of Ͻ30 K.…”

“…For the hole-doped ͑R ,Ca͒MnO 3 systems, a variety of magnetic and transport properties have been observed with decreasing size of R, i.e., FM metallic state, FM insulating state and SG insulating state for R = La, 25 Pr, 26,27 Sm, 27 and Y, [15][16][17][18] respectively. In other words, with decreasing size of the R constituent the FM state gradually gets disfavored.…”

“…[10][11][12][13] At the same time, efforts to dope the metastable phases with carriers have been rarely reported and so far focused on limited A-for-R substitution levels. 12,[14][15][16][17][18] In the present contribution, magnetic and magnetotransport properties are reported for the ͑Lu 1−x Ca x ͒MnO 3 system over the whole Ca-for-Lu substitution range, 0.0Յ x Յ 1.0.…”

Antiferromagnet-ferromagnet phase transition in lightly doped manganites

“…A large difference between the radii lowers, as a rule, the magnetic ordering temperature as a result of competition between various exchange interactions characterized by a large difference in the Mn-O-Mn angles. This is why the spin-glass state sets in in the Sm 1-x Ba x MnO 3 system, wherein the average radius of the Sm and Ba ions is far larger than that between the Y and Ca cations in the Y 1-x Ca x MnO 3 system [32,33]. However, in all rareearth manganites, the Mn 3+ -O-Mn 4+ exchange coupling in the orbitally disordered phase is apparently ferromagnetic.…”

“…However, the orbitally disordered phase in manganites should be ferromagnetic [4,28], whereas we observed a state of the spin-glass type. A direct transition from the antiferromagnetic to the spin-glass phase without passing through the ferromagnetic state was observed to occur in the rare-earth manganites Sm 1-x Ba x MnO 3 and Y 1-x Ca x MnO 3 (x~0.12) [32,33]. It should be pointed out that at approximately this concentration of rare-earth ions, the ferromagnetic-spin glass transition takes place in Bi 1-x Ca x MnO 3 .…”