Magneto-optical investigation of the field-induced spin-glass-insulator to ferromagnetic-metal transition in the bilayer manganite(La0.4Pr0.6)1.2

Jin Xin Cao

¹

,

J. T. Haraldsen

²

,

Ram Rai

³

et al.

Abstract

Magneto-optical investigation of the field-induced spin-glass insulator to ferromagnetic metallic transition of the bilayer manganite (La 0.4 We measured the magneto-optical response of (La0.4Pr0.6)1.2Sr1.8Mn2O7 in order to investigate the microscopic aspects of the magnetic field driven spin-glass insulator to ferromagnetic metal transition. Application of a magnetic field recovers the ferromagnetic state with an overall redshift of the electronic structure, growth of the bound carrier localization associated with ferromagnetic domains, development of a pseudogap, and softening of the Mn-O stretching and bending modes that indicate a structural change. We discuss field-and temperature-induced trends within the framework of the Tomioka-Tokura global electronic phase diagram picture and suggest that controlled disorder near a phase boundary can be used to tune the magnetodielectric response. Remnants of the spin-glass insulator to ferromagnetic metallic transition can also drive 300 K color changes in (La0.4Pr0.6)1.2Sr1.8Mn2O7.

Elastic and magnetic properties of the bilayer manganese oxide(Pr0.6La0.4)1.2Sr1.8Nakanishi1, Shimomura2, Kumagai3 et al. 2007Phys. Rev. B51100View full textAdd to dashboardCite

“…A slight anomaly was observed in both the temperature dependence of the elastic constant and magnetization curve at T * . It is interesting to compare the magnetic properties of the compounds ͑La 1−z Nd z ͒ 22 The measurements did not show any metallic behavior even for magnetic fields up to 10 T in the ferromagnetic metallic state, but, instead, a far-infrared bound carrier excitation was inferred.…”

Optical properties and magnetochromism in multiferroicBiFeO3

“…When charge and spin degrees of freedom are strongly coupled, it is also sensitive to magnetic excitations and spin ordering transitions. 1,2 Magnetochromism, the modification of a material's optical constants with applied magnetic field, 3,4 is an especially important tool for understanding magnetoelectric and multiferroic materials, 5,6 for which spin-charge interaction is expected to be large.…”

Observation of 300K high energy magnetodielectric contrast in the bilayer manganite (La0.4Pr0.6)1.2Sr1.8Mn2O7

“…At the same time, the electromagnetic spectrum is very broad, and the dielectric constant ⑀ 1 is a strong function of energy. 19,20 The ferromagnetic metallic state that is suppressed by chemical pressure in ͑La 0.4 Pr 0.6 ͒ 1.2 Sr 1.8 Mn 2 O 7 is recovered under magnetic field. High energy magnetodielectric ͑HEMD͒ contrast was recently observed in several materials including inhomogeneously mixed-valent K 2 V 3 O 8 ͑ϳ5% at 30 T near 1.2 eV͒, kagome staircase compound Ni 3 V 2 O 8 ͑ϳ16% at 30 T near 1.3 eV͒, and hexagonal multiferroic HoMnO 3 ͑ϳ8% at 20 T near 1.8 eV͒.…”

“…Measurement of the spectroscopic response also provides a way to distinguish between leaky magnetoresistance and true magnetocapacitance because the energies of interest in dielectric spectroscopy are far from the dc limit. 19,20 The parent compound ͑z =0͒ displays a paramagnetic insulator to ferromagnetic metal transition at T c = 120 K. With increasing Pr substitution, T c decreases, and eventually disappears ͑z = 0.6͒, establishing a spin glasslike insulating ground state. This opens the possibility of exploiting changes in ⑀ 1 over a wide energy range, essentially as a multichannel information storage system.…”

“…This opens the possibility of exploiting changes in ⑀ 1 over a wide energy range, essentially as a multichannel information storage system. [20][21][22] The local structure around the Mn centers changes dramatically through the critical field. [12][13][14] In these materials, the HEMD effect derives from spin-lattice-charge mixing.…”