Evolution of the ferromagnetic and nonferromagnetic phases with temperature in phase-separated La1−xSrxCoO3 by high-field La139 NMR

Abstract

We have investigated microscopic magnetoelectronic phase separation and phase evolution with temperature in La 1−x Sr x CoO 3 , for x in the range zero to 0.3, using high-field 139 La NMR. For x ജ 0.1 three coexisting magnetic phases, ferromagnetic (FM), paramagnetic (PM), and spin glass (SG) or cluster glass are observed in the spectra over a wide temperature range. The temperature evolution of the phases shows some conversion of SG to FM phase occurs as the temperature is raised above 30 K. This temperature range coincides with the interval in which Co ions undergo a low-spin (LS) to intermediate-spin (IS) state transition in undoped or very lightly doped material. Measurements on undoped and lightly doped ͑x = 0.03͒ samples provide information on line shape, nuclear relaxation rates, and the LS to IS transition of the Co ions in the PM material. At high temperatures approaching the maximum measured Curie temperature of ϳ240 K, found for x ജ 0.3, the FM phase signal changes and shifts significantly following the magnetization. Evidence for the existence of magnetic entities such as spin polarons coexisting with the PM phase is found at the higher temperatures.

Structural Study of La1–xYxScO3, Combining Neutron Diffraction, Solid-State NMR, and First-Principles DFT Calculations

“…The latter is more favorable for NMR experimentation owing to its half-integer spin quantum number, higher natural abundance (99.91%), and smaller nuclear quadrupole moment ( Q ( 138 La) = 0.45 × 10 –28 m 2 and Q ( 139 La) = 0.20 × 10 –28 m 2 ) . Solid-state 139 La NMR spectroscopy has been applied to a wide variety of systems, including simple lanthanum oxides and halides, , lanthanum-containing zeolites and metallocenes, − and LaF 3 (both single crystals and nanoparticles). , Furthermore, the use of 139 La NMR has been demonstrated in perovskite solid solution type systems such as La 1– x A x MO 3 , where A = Sr, Ca and M = Mn, Cr, and Co. − Using the WURST-QCPMG pulse sequence, , a static wide-line 139 La NMR spectrum was acquired for LaScO 3 (14.1 T) and is shown in Figure S4 in the Supporting Information. The WURST-QCPMG pulse sequence combines the broadband excitation properties of frequency swept WURST pulses − with the signal-to-noise enhancement of the QCPMG protocol, , enabling the rapid acquisition of extremely broad powder patterns.…”

Ferromagnetic state of La1−xBaxCoOFita1, Szymczak2, Puźniak3 et al. 2011Phys. Rev. B271190View full textAdd to dashboardCite

“…This interplay between the variable spin state and the lattice is an additional source of phase separation in cobaltites, exhibiting generally a highly inhomogeneous ground state with coexisting hole-rich FM regions, spin-glass regions, and hole-poor LS regions. 13,14 The coexistence of ferromagnetic and glassy states has been observed in La 1−x Sr x CoO 3 for different doping levels up to x = 0.5. 15,16 The IS state with a partially filled e g level, which therefore is a Jahn-Teller (JT) active state, plays a crucial role in the ferromagnetic state of cobaltites.…”

Photo-induced Antiferromagnetic-ferromagnetic and Spin-state Transition in GdBaCo2O5.5 Thin Film

“…Note that our GBCO film has finite magnetization in the AFM phase, which should be attributed to the competition between AFM and FM exchange interactions, either the canting of AFM moments [15] or the coexistence of AFM and FM phases [26,27]. The experimental setups of TR-XMCDR and TR-RMXD is schematically shown in Fig.…”