Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userElectron magnetic resonance studies of nanomanganite Nd0.67Sr0.33MnO3
76
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Nd_0.67Sr_0.33MnO_3 nanoparticles with the grain size of about 30 nm are prepared by sol-gel method.These nanopowders are annealed at four different temperatures viz. 800 oC, 900 oC, 1000 oC and 1100 oC to study the effect of particle size on magnetic, transport and electron magnetic resonance (EMR) spectral parameters. The samples are characterized by XRD, SEM, EDAX and TEM. The ac susceptibility experiments show that as the particle size increases the ferromagnetic to paramagnetic transition temperature (Tc) decreases. The metal-insulator transition temperature also changes with the particle size as revealed by resistivity measurements. EMR spectra of the nanopowders are recorded from room temperature down to 4K using an X-band EPR spectrometer. the spectra could be fitted using two broad-Gaussian lineshapes below Tc and suggested the ferromagnetic nature of the samples. Above Tc a single Lorenzian fits the signals as expetced for paramagnetic samples. The EMR spectral parameters are found to be different from the bulk (polycrystalline)sample data. The spectral parameters show variation with the particle size. The presence of the two signals in the ferromagnetic phase is attributed to core and shell regions in the nanoparticles. We could estimate the shell thickness from the EMR intensity data as 0.7 - 1 nm which agrees with other measurements.
rate research
Read More
We study the effects of 10% Cr substitution in Mn sites of Bi0.5Sr0.5MnO3 on the antiferromagnetic (AFM) (TN ~ 110 K) transition using structural, magnetic and electron paramagnetic resonance (EPR) techniques. Field cooled (FC) and zero field cooled (ZFC) magnetization measurements done from 400 K down to 4 K show that the compound is in the paramagnetic (PM) phase till 50 K where it undergoes a transition to a short range ferromagnetic phase (FM). Electron paramagnetic resonance measurements performed in the temperature range 300 K till 80 K conform with the magnetization measurements as symmetric signals are observed owing to the paramagnetic phase. Below 80 K, signals become asymmetric. Electron paramagnetic resonance intensity peaks at ~ 110 K, the decreasing intensity below this temperature confirming the presence of antiferromagnetism. We conclude that below 50 K the magnetization and EPR results are consistent with a cluster glass phase of BSMCO, where ferromagnetic clusters coexist with an antiferromagnetic background.
High mobility two-dimensional electron gases (2DEGs) underpin todays silicon based devices and are of fundamental importance for the emerging field of oxide electronics. Such 2DEGs are usually created by engineering band offsets and charge transfer at heterointerfaces. However, in 2011 it was shown that highly itinerant 2DEGs can also be induced at bare surfaces of different transition metal oxides where they are far more accessible to high resolution angle resolved photoemission (ARPES) experiments. Here we review work from this nascent field which has led to a systematic understanding of the subband structure arising from quantum confinement of highly anisotropic transition metal d-states along different crystallographic directions. We further discuss the role of different surface preparations and the origin of surface 2DEGs, the understanding of which has permitted control over 2DEG carrier densities. Finally, we discuss signatures of strong many-body interactions and how spectroscopic data from surface 2DEGs may be related to the transport properties of interface 2DEGs in the same host materials.
We report on the magnetic resonance of NH_3K_3C_60 powders in the frequency range of 9 to 225 GHz. The observation of an antiferromagnetic resonance below the phase transition at 40 K is evidence for an antiferromagnetically ordered ground state. In the normal state, above 40 K, the temperature dependence of the spin-susceptibilty measured by ESR agrees with previous static measurements and is too weak to be explained by interacting localized spins in an insulator. The magnetic resonance line width has an unusual magnetic-field dependence which is large and temperature independent in the magnetically ordered state and decreases rapidly above the transition. These observations agree with the suggestion that NH_3K_3C_60 is a metal in the normal state and undergoes a Mott-Hubbard metal to insulator transition at 40 K.
The CeIn3-xSnx cubic heavy fermion system presents an antiferromagnetic transition at T_N = 10 K, for x = 0, that decreases continuously down to 0 K upon Sn substitution at a critical concentration of x_c ~ 0.65. In the vicinity of T_N -> 0 the system shows non-Fermi liquid behavior due to antiferromagnetic critical fluctuations. For a high Sn content, x > 2.2, intermediate valence effects are present. In this work we show that Gd3+-doped electron spin resonance (ESR) probes a change in the character of the Ce 4f electron, as a function of Sn substitution. The Gd3+ ESR results indicate a transition of the Ce 4f spin behavior from localized to itinerant. Near the quantum critical point, on the antiferromagnetic side of the magnetic phase diagram, both localized and itinerant behaviors coexist.
We study and compare magnetic and electron paramagnetic resonance behaviors of bulk and nanoparticles of Nd(1-x)CaxMnO3 in hole doped (x = 0.4;NCMOH) and electron doped (x = 0.6;NCMOE) samples. NCMOH in bulk form shows a complex temperature dependence of magnetization M(T), with a charge ordering (CO) transition at around 250 K, an antiferromagnetic (AFM) transition at around 150 K and a transition to a canted AFM phase/mixed phase at around 80 K. Bulk NCMOE behaves quite differently with just a charge ordering transition at around 280 K, thus providing a striking example of the so called electron-hole asymmetry. While our magnetization data on bulk samples are consistent with the earlier reports, the new results on the nanoparticles bring out drastic effects of size reduction. They show that M(T) behaviors of the two nano samples are essentially similar in addition to the absence of the charge order in them thus providing strong evidence for vanishing of the electron-hole asymmetry in nanomanganites. This conclusion is further corroborated by electron paramagnetic resonance studies which show that the large difference in the g-values and their temperature dependence found for the two bulk samples disappears as they approach a common behavior in the corresponding nano samples.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
