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To develop and validate a fast, robust, isocratic reversed-phase high performance liquid chromatographic method for the determination of bisoprolol in bulk and pharmaceutical formulations.Optimum separation of bisoprolol was achieved using as stationary phase a Zorbax SB-C18 column (100×3 mm; 5µm). The mobile phase was a mixture of phosphate buffer (pH = 3.5) and acetonitrile (70:30) with a flow rate of 1mL/min. The UV detection was performed at 225nm. The temperature of the column and autosampler was 25°C. The specificity was assessed by using metoprolol as internal standard. The method was validated in accordance with the current ICH guidelines in terms of linearity, limit of detection, limit of quantification, precision, accuracy, recovery and system suitability.The retention time for bisoprolol was 1.158 minute. The calibration graph was linear in the concentration range 5-90 µg/mL. The LOD and LOQ of bisoprolol were 1.63 μg/mL and 4.94 μg/mL, respectively. The intra and interday precision of measurements were lower than the accepted criteria (RSD ≤ 2%). The recovery values of HPLC determination of bisoprolol from tablets proved that none of the excipients influenced the results of the analysis.The assay it was found to be accurate, reproducible, sensitive and less time consuming. The proposed method can be successfully applied to quality control studies of pharmaceutical products.

The cooper(II) complex combination of N, N'-disalicylidenemethylenediamine and the Schiff bis base were investigated for anti-inflammatory activity.In vivo, the anti-inflammatory activity of the metallic complex in comparison with the activity of the Schiff bis base was tested by the method of Winter and co-workers using the Levy technique.Our study on the anti-inflammatory activity of a new Schiff bis base and its complex cooper(II) combination showed that the Schiff bis bases exhibited significant anti-inflammatory action in acute experimental inflammation when compared to the control group. The copper cation from the complex combination enhanced the anti-inflammatory effect of the Schiff bis base, the effect being stronger at doses of 10 mg/kg cooper(II) complex.The Schiff bis base and its cooper(II) complex had an anti-inflammatory effect comparable to that of indomethacin.

We report on the scaling behaviour of the colossal negative magnetoresistance effect (CMR) in a single crystal of the bilayer manganite (La0.4Pr0.6)1.2Sr1.8Mn2O7. The high Pr content is responsible for the absence of long-range ferromagnetism and for a CMR effect in the order of 106. The system is down to the Neel temperature (TN = 50 K) in a superparamagnetic state with spin clusters extending over 6–9 unit cells. The coefficient C, which describes the magnetization-induced resistance drop in the paramagnetic state, has absolute values up to C = 15 at 100 K. The temperature dependence C T−1 is explained by spin-dependent hopping between magnetic clusters. Spin-dependent scattering and Kondo-lattice models do not account for the magnitude of C and its variation with temperature.

Bisoprolol fumarate is prescribed for the treatment of hypertension and angina pectoris.The purpose of this study was to develop a simple, sensitive, accurate, and reproducible method for estimation of bisoprolol fumarate in tablets.The proposed method was based on a yellow colored complex formed with tropaeolin 00, extractable in dichloromethane with maximum absorbance at 412 nm. The method was validated statistically.The linearity domain was observed in the concentration of 5-30 microg/ml. The recovery studies confirmed the accuracy of the proposed method.The proposed method can be applied for the routine analysis of bisoprolol from formulations.

Thermal expansion and magnetostriction both in the a b -plane and along the c -axis of double-layered perovskite manganite (La 1- z Pr z ) 1.2 Sr 1.8 Mn 2 O 7 ( z =0, 0.2, 0.4 and 0.6) single crystals have been measured as a function of temperature and magnetic field. The anomalous lattice distortion and the giant magnetostriction associated with the CMR were observed near the PI to FM transition temperature T c . These findings indicate that the PI to FM transition and the CMR near T c are not associated with the anisotropic lattice striction concerning the static John–Teller effect but with the negative volume striction related to the delocalization of polarons to itinerant carriers.

Radio frequency magneto-impedance measurements clearly reveal a pronounced anomaly at 260K besides the main MI transition at 125K in the double perovskite material $La_{1.2}Sr_{1.8}Mn_{2}O_{7}$. This feature is not seen clearly in static resistivity and magnetization measurements. We suggest that this anomaly represents short range magnetic correlations enhanced at radio frequencies, with the easy axis along the c-axis .

Bisoprolol is a drug belonging to beta blockers drugs used primarily for the treatment of cardiovascular diseases.A spectrophotometric method for quantitative determination of bisoprolol was developed based on the formation of a complex combination between bisoprolol and picric acid.The complex combination of bisoprolol and picric acid has a maximum absorbance peak at 420 nm. Optimum working conditions were established and the method was validated.The method presented a good linearity in the concentration range 5-120 microg/ml (regression coefficient r2 = 0.9992). The RSD for the precision of the method was 1.74 and for the intermediate precision 1.43, and recovery values ranged between 98.25-101.48%.The proposed and validated spectrophotometric method for the determination of bisoprolol is simple and cost effective.

We have established a magnetic phase diagram of (La1−zPrz)1.2Sr1.8Mn2O7 for z=0.6 by means of magnetization measurements. The magnetization curve exhibits a rectangular hysteresis loop below T ∗ , implying the ferromagnetic behavior. A metamagnetic transition was observed also above T ∗ without a hysteresis. Combined with our previous data of the elastic constants, it was found that there were mainly three magnetic phases in the Field–Temperature (H–T) phase diagram. The magnetic properties of (La1−zPrz)1.2Sr1.8Mn2O7 for z=0.6 at low temperatures is discussed in terms of spin- and orbital-glass state.

We have studied the effect of pressure on the anomalous lattice striction, both in the ab-plane and along the c-axis, of (La,Pr)(1.2)Sr(1.8)Mn(2)O(7) single crystals over the temperature region where the paramagnetic insulator to ferromagnetic metal transition takes place. We have examined the temperature dependence of the resistivity and the magnetization under applied pressure. The chemical pressure effect due to Pr-substitution at the La site suppresses the transition temperature of the parent crystal, while the application of external pressure on Pr-substituted crystals enhances the double exchange driven metallic state, resulting in a stable rise of T(c).

In order to analyze lisinopril using a selective membrane electrode, the electro-active compound was obtained and included in the selective membrane. The new analysis method was developed and validated.The electro-active compound was obtained through the precipitation of lisinopril in acidic media using silicowolframic acid solution. The membrane was obtained by mixing the electro-active compound with polyvinylchloride using tetrahydrofurane as solvent. The solution was evaporated in order to obtain a thick membrane, which was then attached at one end of a polyvinylchloride tube. The internal Ag/AgCl reference electrode was inserted in that tube. The assembly was filled with a lisinopril internal solution. The electrode was characterized by establishing the following characteristics: electrode slope, selectivity, optimal pH range, response time and life-time period. The developed method was validated.The method showed a good linearity in the range of 10(-7) and 10(-2)M (the correlation coefficient r = 0.9991). The detection limit (LD) was 8,66 x 10(-8)M and the quantification limit (LQ) was 7,8 x 10(-7)M. There were established the precision (RSD = 1.73%) and the accuracy (mean recovery was 99.92%)The experimental results demonstrated a good sensibility.

Aflatoxins and sterigmatocystin are potent carcinogens, certainly involved in pathogenesis of liver cancer.To evaluate the risk of mycotoxin intake and to determine the presence of aflatoxin B1 (AFB1) and sterigmatocystin (STC) in patients with liver cirrhosis.The study included 92 patients (33 controls, 59 liver cirrhosis) that completed a food frequency questionnaire (FFQ). Blood and urine samples were collected and mycotoxins determined by high performance liquid chromatography.18.18% samples in controls and 72.88% in cirrhosis group presented detectable levels of mycotoxins. The mean values of AFB1 in blood were 0.7 ng/mL in controls and 1.67 ng/mL in test group (p = 0.11); STC presented 60 times higher levels in second group (p0.01). AFB1 presented a mean level of 1.2 ng/mL in urine of test group (not detected in controls); STC presented 256 time higher concentration in urine of cirrhotic patients, with a perfect correlation between blood and urine levels in control (r=1) and no correlation in test group (r = 0.05). There were no correlations between mycotoxin, liver enzymes, alpha-fetoprotein and mycotoxin intake risk estimated by FFQ.Most of the patients presented detectable levels of mycotoxins, significantly increased in cases with liver cirrhosis, probable due to a specific metabolic pattern.

We have investigated glassy magnetic freezing in(La₀.₄Pr₀.₆)₁.₂Sr₁.₈Mn₂O₇ single crystals together with the field-induced transition to a metastable ferromagnetic phase using ac magnetic susceptibility and heat capacity measurements. The magnetization measurements show evidence for the development of a zero-field glassy ground state below 45 K along with a hysteretic, field-induced change in susceptibility associated with the transition to the ferromagnetic phase above 5 T. The heat capacity develops a clear peak at higher temperatures with the application of large magnetic fields, consistent with the development of a ferromagnetic order, while at low temperatures the Sommerfeld coefficient is monotonically reduced by an applied field, suggesting suppression of spin fluctuations. The heat capacity shows hysteretic behaviour, accompanied by a sharp decrease at a critical field, when held at fixed temperature, which does not recover on reducing the field back to zero. These measurements suggest that the zero-field ground state for (La₀.₄Pr₀.₆)₁.₂Sr₁.₈Mn₂O₇ consists of frozen disordered spin clusters, which develop into a metastable ferromagnetic state in modest magnetic fields.

Lisinopril is a drug of the angiotensin converting enzyme (ACE) inhibitor class that is primarily used in treatment of hypertension, congestive heart failure, heart attacks and also in preventing renal and retinal complications of diabetes. We compared the dissolution profiles of Lisinopril 20 mg tablets (Antibiotice S.A. laşi) and Zestril 20 mg tablets (Astra Zeneca).Because lisinopril is a third class active substance, we performed dissolution tests in standard media at three pH values: 1.2, 4.5 and 6.8 using the paddle apparatus at 75 rpm.Both pharmaceutical formulations present a dissolution percentage more than 85% (Q) of the labeled amount.Both pharmaceutical formulations present similar dissolution profile. Key words

The transport, magnetic, and thermal properties of single crystal double-layer manganites of the Ruddlesden-Popper series (La1−z Prz)1.2Sr1.8Mn2O7 (z=0.1 or 0.4) were studied. The compounds exhibit the colossal negative magnetoresistance effect in the region of a transition into a ferromagnetic state. Upon the isoelectronic substitution of Pr3+ for La3+, the Curie temperature decreases, while the easy magnetization axis rotates from the ab plane to the c axis. The observed effect is related to a change in the occupancy of $$d{x^2-y^2} $$ and $$d{3z^2-r^2} $$ orbitals as a result of stretching of the MnO6 octahedra.

Magnetization, magnetoresistance (MR), thermal expansion and magnetostriction (MS) measurements both in the ab- plane and along the c -axis of (La 1 −z Pr z ) 1.2 Sr 1.8 Mn 2 O 7 ( z= 0; 0.2) single crystals are reported. The substitution by Pr ( z= 0.2) decreased the T c from ∼120 K to ∼95 K but also drastically changed the sign of the MS along the c -axis near T c . A large MS was found to accompany the MR.

PVC matrix membrane selective electrodes for ranitidine, nizatidine and famotidine, based on sparingly soluble complexes, were prepared and characterized. The optimum functional pH range, response time, selectivity and lifetime were determined for each of the built electrodes. The linear range, precision and accuracy of each method were obtained by statistical interpretation of experimental results, while the limit of detection and thelimit of quantification were determined by a graphical method. All these electrodes were applied for the direct quantitative potentiometric determination of ranitidine hydrochloride, nizatidine and famotidine in pharmaceutical formulations.

We report the effect of pressure on the steplike magnetostriction of single crystalline bilayered manganite ${({\text{La}}_{0.4}{\text{Pr}}_{0.6})}_{1.2}{\text{Sr}}_{1.8}{\text{Mn}}_{2}{\text{O}}_{7}$, for our understanding of the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator to a ferromagnetic metal phase. The application of pressure suppresses a steplike transformation and causes a broad change in the magnetostriction. The injection of an electric current to the crystal also weakens the steplike variation in both the magnetostriction and magnetoresistance. The stabilization of ferromagnetic interaction or the delocalization of charge carriers is promoted with the applied pressure or applied current, resulting in the suppressed steplike behavior. Our findings suggest that the step phenomenon is closely related to the existence of localized carriers such as the short-range charge-orbital-ordered clusters.

A sensible and rapid spectrophotometric assay for adrenaline was developed.The method is based on the reaction with ammonium molybdate and sodium nitrite in acid medium.The obtained compound is stable, soluble in water and has the absorbtion maximum at 405 nm. Beer's law is valid within a concentration range of 20-160 microg/mL. The validity of the method was tested by statistical analysis of the experimental data using the linearity, the scale's calibration factor, the detection limit, the quantification limit and the precision.A new method for the assay of adrenaline in pharmaceutical products has been developed.

Phosphotungstic acid forms salt type ionic association complexes with a large number of medicinal drugs that contain cation forming proton acceptor moieties.Ranitidine, nizatidine and famotidine complexes with phosphotungstic acid were synthesized and subsequently characterized by their melting point, water solubility, specific absorbance, UV spectra and IR spectra.These sparingly soluble complexes were applied for the fabrication of membrane selective electrodes for quantitative potentiometric determination of ranitidine, nizatidine and famotidine.There have been synthesized phosphotungstic acid complexes with uses in fabrication of membrane selective electrodes for quantitative potentiometric determination of ranitidine, nizatidine and famotidine.

This paper proposes a new method for the quantitative determination of famotidine, based on its reaction with phosphomolybdic acid. The measurements were carried out at wavelength of 400 nm. This method has been validated and it has been applied to the determination of famotidine in pharmaceutical products.

We report a steplike lattice transformation of single crystalline $({\mathrm{La}}_{0.4}{\mathrm{Pr}}_{0.6}{)}_{1.2}{\mathrm{Sr}}_{1.8}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ bilayered manganite accompanied by both magnetization and magnetoresistive jumps, and examine the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator to a ferromagnetic metal phase accompanied by a huge decrease in resistance. Our findings support that the abrupt magnetostriction is closely related to an orbital frustration existing in the inhomogeneous paramagnetic insulating phase rather than a martensitic scenario between competing two phases.

We have studied the pressure effect on magnetostriction, both in the $ab$ plane and along the $c$ axis of a ${(\mathrm{La},\mathrm{Pr})}_{1.2}{\mathrm{Sr}}_{1.8}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ bilayered manganite single crystal over the temperature region where the field-induced ferromagnetic metal (FMM) transition takes place. For comparison, we have also examined the pressure dependence of magnetization curves at the corresponding temperatures. The applied pressure reduces the critical field of the FMM transition and it enhances the remanent magnetostriction. An anomalous pressure effect on the remanent lattice relaxation is observed and is similar to the pressure effect on the remanent magnetization along the $c$ axis. These findings are understood from the viewpoint that the double-exchange interaction-driven FMM state is strengthened by the application of pressure.

We report a steplike lattice transformation of single crystalline (La0.4Pr0.6)1.2Sr1.8Mn2O7 bilayered manganite accompanied by both magnetization and magnetoresistive jumps, and examine the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator to a ferromagnetic metal phase accompanied by a huge decrease in resistance. Our findings support that the abrupt magnetostriction is closely related to an orbital frustration existing in the inhomogeneous paramagnetic insulating phase rather than a martensitic scenario between competing two phases.

We measured the magneto-optical response of (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$ 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 (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$.

Famotidine, belonging to H2-antagonist group, is a compound containing a thiazolic moiety and it is used in peptic ulcer therapy. This paper debates the possibility of developing a new ultraviolet spectrophotometric assessment by using the reaction between famotidine and picrolonic acid. We carried out our determinations at 362 nm, where the absorbency of famotidine - picrolonic acid complex is maximal, and we have established the optimal reaction conditions. This method was successfully applied for famotidine assay from pharmaceutical dosage forms.

We investigated the effect of pressure on the magnetic properties of a single crystal of the bilayer manganese oxide (Pr0.6La0.4)1.2Sr1.8Mn2O7 by means of DC magnetization measurements under pressure. The ferromagnetic transition, which is accompanied by a metal–insulator transition, is highly sensitive to pressure. The pressure causes a structural variation, which affects the magnetic properties. We discuss the pressure dependence of the 3d electronic state of the Mn ion in this system.

We have investigated magnetic, electrical, and thermal transport properties (Seebeck effect and thermal conductivity) of ${\mathrm{LaSr}}_{2}{\mathrm{Mn}}_{2\ensuremath{-}y}{\mathrm{Cr}}_{y}{\mathrm{O}}_{7}$ polycrystalline samples ($y=0.1$, 0.2, 0.4, and 0.6). The ${\mathrm{Cr}}^{3+}$ substitution for ${\mathrm{Mn}}^{3+}$ sites causes a removal of ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ orbital of ${e}_{g}$ electron, resulting in a volume shrinkage of the lattice. Magnetic measurements reveal the appearance of a glassy behavior for Cr-doped samples, accompanied by both a collapse of the A-type antiferromagnetic structure and the growth of ferromagnetic clusters. Cr-doping effect on electrical transport strongly enhances an insulating behavior over a wide range of temperatures, while it suppresses a local minimum of thermoelectric power at lower temperatures. For all polycrystalline samples with Cr substitution, the variable-range-hopping conduction model gives a reasonable fit to both resistivities and Seebeck coefficients. The phonon thermal conduction gradually rises with increasing Cr content, which is in contrast to a typical impurity effect on thermal conductivity. We attribute this to a suppression of local lattice distortion through the introduction of Jahn-Teller inactive ions of ${\mathrm{Cr}}^{3+}$.

We have investigated the resistive relaxation of a ${({\mathrm{La}}_{0.4}{\mathrm{Pr}}_{0.6})}_{1.2}{\mathrm{Sr}}_{1.8}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ single crystal, in order to examine the slow dynamics of the field-induced insulator-to-metal transition of bilayered manganites. The temporal profiles observed in remanent resistance follow a stretched exponential function accompanied by a slow relaxation similar to that observed in magnetization and magnetostriction data. We demonstrate that the remanent relaxation in magnetotransport has a close relationship with magnetic relaxation that can be understood in the framework of an effective-medium approximation by assuming that the first-order parameter is proportional to the second-order one.

We have investigated the time dependence of remanent magnetostriction in a ${(\mathrm{La},\mathrm{Pr})}_{1.2}{\mathrm{Sr}}_{1.8}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ single crystal in order to examine the slow dynamics of lattice distortion in bilayered manganites. A competition between double-exchange and Jahn-Teller-type orbital-lattice interactions results in the observed lattice profile following a stretched exponential function. This finding suggests that spatial growth of the local lattice distortions coupled with ${e}_{g}$-electron orbital strongly correlates with the appearance of the field-induced colossal magnetoresonance effect.

The bilayer manganite La1.2Sr1.8Mn2O7 exhibits a phase transition from a paramagnetic insulating (PI) to a ferromagnetic metallic (FM) state with a colossal magnetoresistance (CMR) effect. Upon 60% Pr substitution, magnetic order and PI to FM transition are suppressed. Application of a moderate magnetic field restores an FM state with a CMR effect. Neutron scattering by a single crystal of (La0.4Pr0.6)1.2Sr1.8Mn2O7, under a magnetic field of 5 T, has revealed a long-range and homogeneous ferromagnetic order. In the PI phase, under zero field, correlated lattice polarons have been detected. At 28 K, under 5 T, the spin wave dispersion curve determines an in-plane isotropic spin wave stiffness constant of 146 meV A(2). So the magnetic field not only generates a homogeneous ferromagnetic ground state, but also restores a magnetic coupling characteristic of FM CMR manganites.

We investigate the polarized magneto-optical response of ${({\mathrm{La}}_{0.4}{\mathrm{Pr}}_{0.6})}_{1.2}{\mathrm{Sr}}_{1.8}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ in order to reveal the microscopic nature of the states involved in the field-induced paramagnetic semiconductor to ferromagnetic metal transition. We find significant changes in the electronic structure of the title compound under magnetic fields due to the evolution of the Jahn-Teller-split ${\mathrm{Mn}}^{3+}\phantom{\rule{0.3em}{0ex}}{e}_{g}$ orbitals. Consequences of this field-induced modification of the $d$ orbitals include the substantial colossal magnetoresistence effect, unusual magnetic relaxation behavior, and a change in orbital occupation. Based upon the directional dependence of the magneto-optical spectra, we demonstrate that the high-field ferromagnetic state is homogeneous.

The bilayer manganite La1.2Sr1.8Mn2O7 exhibits a phase transition from a paramagnetic insulating (PI) to a ferromagnetic metallic (FM) state with a colossal magnetoresistance (CMR) effect. Upon 60% Pr substitution, magnetic order and PI to FM transition are suppressed. Application of a moderate magnetic field restores an FM state with a CMR effect. Neutron scattering by a single crystal of (La0.4Pr0.6)1.2Sr1.8Mn2O7, under a magnetic field of 5 T, has revealed a long-range and homogeneous ferromagnetic order. In the PI phase, under zero field, correlated lattice polarons have been detected. At 28 K, under 5 T, the spin wave dispersion curve determines an in-plane isotropic spin wave stiffness constant of 146 meV A(2). So the magnetic field not only generates a homogeneous ferromagnetic ground state, but also restores a magnetic coupling characteristic of FM CMR manganites.

Ranitidine, belonging to H2-antagonist group, is a compound containing a furanic moiety and is used in peptic ulcer therapy. This paper debates the possibility of developing a new visible spectrophotometric assessment by using the reaction between ranitidine and eosine. We carried out our determinations at 505 nm, where the absorbency of ranitidine-eosine complex is maximal, and we have established the optimal reaction conditions. This method was successfully applied for ranitidine assay from pharmaceutical dosage forms.

One membrane-selective electrode with PVC matrix for atropine is described, with atropine tetraphenylborate as electroactive material. This electrode has a linear response in the concentration range of 10(-2)-10(-5) M atropine sulphate, with a detection limit of 3.29 x 10(-6) M. This electrode was used with good results for quantitative assay by direct potentiometry and potentiometric titration of atropine sulphate from pharmaceutical formulations.

Unpolarized and polarized neutron diffraction measurements have been carried out on the bilayer manganite (La 0 . 4 Pr 0 . 6 ) 1 . 2 Sr 1 . 8 Mn 2 O 7 which undergoes simultaneous semiconductor-metal paraferro-magnetic transitions under magnetic field. Maximum entropy magnetization density reconstruction and multipole refinement on flipping ratios evidence the existence of two distinct field-induced states. The field-induced ferromagnetic state where the field is parallel to the c axis is characterized by the presence of magnetic moment on the Sr site of 0.48(2)μ B , due to the Pr substitution. It also shows a high population of the d 3 z 2 - r 2 orbitals of Mn 3 + . For the field-induced state where the field is parallel to the a or b axes no magnetization density was found at the Sr site and the d x 2 - y 2 orbital is slightly more populated than the d 3 z 2 - r 2 one.

Unpolarized and polarized neutron diffraction measurements have been carried out on the bilayer manganite (La0.4Pr0.6)1.2Sr1.8Mn2O7 which undergoes simultaneous semiconductor-metal paraferromagnetic transitions under magnetic field. Maximum entropy magnetization density reconstruction and multipole refinement on flipping ratios evidence the existence of two distinct field-induced states. The field-induced ferromagnetic state where the field is parallel to the c axis is characterized by the presence of magnetic moment on the Sr site of 0.48(2)mu(B), due to the Pr substitution. It also shows a high population of the d3(z(2)-r(2)) orbitals of Mn3+. For the field-induced state where the field is parallel to the a or b axes no magnetization density was found at the Sr site and the dx(2)(-y(2)) orbital is slightly more populated than the d3(z(2)-r(2)) one.

We report on the low-temperature resistance and magnetization of a single crystal of the bilayer manganite $({\mathrm{La}}_{0.4}{\mathrm{Pr}}_{0.6}{)}_{1.2}{\mathrm{Sr}}_{1.8}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}.$ In zero field the sample is an insulator at all temperatures while at fields larger than 3 T a transition to a ferromagnetic metallic state is observed. Below 50 K the sample shows a pronounced memory effect, in which both resistivity and magnetization become dependent on the magnetic history and clearly demonstrate hysteretic behavior. At these low temperatures a difference in zero-field resistivity before and after magnetization of six orders of magnitude has been measured. The relaxation of the memory effect follows a stretched exponential function with a characteristic decay time of 5 hours at 10 K, which decreases to less than 1 ms above 40 K. These low-temperature properties can be related to magnetostriction data, indicating the presence of a field-induced change in the orbital occupancy of the ${e}_{g}$ electrons of ${\mathrm{Mn}}^{3+}.$

We present the experimental results of DC magnetization measurements on the bilayer manganese oxide (Pr 0.6 La 0.4 ) 1.2 Sr 1.8 Mn 2 O 7 under pressure. The data were taken to elucidate the magnetic properties of the field-induced ferromagnetic phase and to establish the magnetic phase diagram on the fields applied along the c -axis. The results indicated that the phase is sensitive to the applied pressure. The isothermal remanent magnetization M IRM ( t ) as a function of time t in the ferromagnetic phase suggests the existence of the relaxation process and its pressure effect. It seems that the effect of pressure leads to a variation of the transition probability between the ferromagnetic metal and paramagnetic insulating state.

We have carried out thermoelectric power (S), magnetization and magnetoresistance measurements on LaSr2Mn2−yCryO7 compounds (y=0.1, 0.2 and 0.4). In the bilayer manganite LaSr2Mn2O7 (hole doping level x= 1 2 ), it is well known that the coexistence of metallic A-type antiferromagnetic (AF) phase and CE-type charge/orbital order (CO/OO) phase is essential to understand physical properties. The Cr-doping strongly suppressed the AF transition temperature and its associated peak in S down to lower temperatures. The Cr impurities on the Mn site in the bilayer manganite system did not cause such a dramatic influence as the insulator to metal transition in cubic manganites. This finding is discussed on the basis of phase separation model concerning the A-type majority and CE-type minority phases.

We have investigated glassy magnetic freezing in(La₀.₄Pr₀.₆)₁.₂Sr₁.₈Mn₂O₇ single crystals together with the field-induced transition to a metastable ferromagnetic phase using ac magnetic susceptibility and heat capacity measurements. The magnetization measurements show evidence for the development of a zero-field glassy ground state below 45 K along with a hysteretic, field-induced change in susceptibility associated with the transition to the ferromagnetic phase above 5 T. The heat capacity develops a clear peak at higher temperatures with the application of large magnetic fields, consistent with the development of a ferromagnetic order, while at low temperatures the Sommerfeld coefficient is monotonically reduced by an applied field, suggesting suppression of spin fluctuations. The heat capacity shows hysteretic behaviour, accompanied by a sharp decrease at a critical field, when held at fixed temperature, which does not recover on reducing the field back to zero. These measurements suggest that the zero-field ground state for (La₀.₄Pr₀.₆)₁.₂Sr₁.₈Mn₂O₇ consists of frozen disordered spin clusters, which develop into a metastable ferromagnetic state in modest magnetic fields.

We report a significant decrease in the low-temperature resistance induced by the application of an electric current on the $ab$-plane in the paramagnetic insulating (PMI) state of (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$. A colossal electroresistance effect attaining -95% is observed at lower temperatures. A colossal magnetoresistive step appears near 5T at low temperatures below 10K, accompanied by an ultrasharp width of the insulator-metal transition. Injection of higher currents to the crystal causes a disappearance of the steplike transition. These findings have a close relationship with the presence of the short-range charge-ordered clusters pinned within the PMI matrix of the crystal studied., 4 pages 3 figures

We report the pressure effect on a steplike magnetostriction of single crystalline (La0.4 Pr0.6)1.2Sr1.8Mn2O7 bilayered manganite, for our understandings of the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator to a ferromagnetic metal phase. Application of pressure suppresses a steplike transformation and causes a broad change in the magnetostriction. A delocalization of carriers is promoted with the applied pressure, resulting in the suppressed steplike behavior. The steplike behavior observed is closely related to the existence of localized carriers.

Large high energy magnetodielectric effects are observed in the bilayer manganite (La0.4Pr0.6)1.2Sr1.8Mn2O7, a direct consequence of exploiting magnetoresistance changes associated with the field driven spin-glass insulator to ferromagnetic metal transition and its high temperature remnant. The low temperature magnetodielectric contrast is as large as ∼100% near 0.8eV at 10T and over 10 000% in selected phonon regions. The 300K magnetodielectric contrast is ∼20% near 1.1eV at 30T. The results are potentially useful for magnetic memory applications away from the dc limit.