Field-Induced Magnetization Steps in Intermetallic Compounds and Manganese Oxides: The Martensitic Scenario

Field-induced magnetization jumps with similar characteristics are observed at low temperature for the intermetallic germanide Gd5Ge4and the mixed-valent manganite Pr0.6Ca0.4Mn0.96Ga0.04O3. We report that the field location -and even the existence- of these jumps depends critically on the magnetic field sweep rate used to record the data. It is proposed that, for both compounds, the martensitic character of their antiferromagnetic-to-ferromagnetic transitions is at the origin of the magnetization steps.Comment: 4 pages,4 figure

Formation of finite antiferromagnetic clusters and the effect of electronic phase separation in Pr{_0.5}Ca{_0.5}Mn{_0.975}Al{_0.025}O{_3}

We report the first experimental evidence of a magnetic phase arising due to the thermal blocking of antiferromagnetic clusters in the weakened charge and orbital ordered system Pr{_0.5}Ca{_0.5}Mn{_0.975}Al{_0.025}O{_3}. The third order susceptibility (\chi_3) is used to differentiate this transition from a spin or cluster glass like freezing mechanism. These clusters are found to be mesoscopic and robust to electronic phase separation which only enriches the antiphase domain walls with holes at the cost of the bulk, without changing the size of these clusters. This implies that Al substitution provides sufficient disorder to quench the length scales of the striped phases.Comment: 4 Post Script Figure

Staircase-like metamagnetic transitions in phase-separated manganites: influence of thermal and mechanical treatments

Substitutions in the Mn-sublattice of antiferromagnetic, charge and orbitally ordered manganites was recently found to produce intriguing metamagnetic transitions, consisting of a succession of sharp magnetization steps separated by plateaus. The compounds exhibiting such features can be divided in two categories, depending on whether they are sensitive to thermal cycling effects or not. One compound of each category has been considered in the present study. The paper reports on the influence of two treatments: high-temperature annealing and grinding. It is shown that both of these treatments can drastically affect the phenomenon of magnetization steps. These results provide us with new information about the origin of these jumps in magnetization.Comment: accepted for publication in J.Appl.Phy

Relationship between structure and deposition conditions for CuInO2 thin films

CuInO2 thin films were deposited using the Pulsed Laser Deposition technique. The influence of various deposition parameters and mainly the oxygen pressure on the texture, composition and structure of the films is discussed. Films deposited with an oxygen pressure in the 0.2-1 Pa range exhibit the delafossite structure. Higher pressure introduces an increase in the oxygen content leading to a CuInO2.10 composition for the film deposited at 5 Pa and a progressive loss of the delafossite structure. As confirmed by an EXAFS study, the oxygen stoichiometry controls the Cu+/ Cu2+ ratio

An NMR study of Pr0.5Ca0.5Mn1-xGaxO3 (X=0 and 0.03)

An NMR study of polycrystalline Pr(0.5)Ca(0.5)Mn(1-x)GaxO(3) (x = 0 and 0.03) at 3 K is presented. Zero field spin-echo spectra of the Ga doped compound consist of an overlapping Ga-69,Ga-71 signal at 74 MHz (hyperfine field of 5.3 T), a Mn-55 double exchange line at 375 MHz (35.5 T) and a weak Mn3+ signal between 400 and 550 MHz. Measurements in an applied field show a step-like increase in the double exchange line intensity, which corresponds to an increase in the amount of the ferromagnetic metallic phase. This coincides with a step-like feature in the bulk magnetization measurements. The effect is similar to that in the previous field dependent Mn-55 NMR measurements of Pr0.67Ca0.33MnO3. At the demagnetized and remanent state, a variation of spin-spin relaxation time, T-2, across the Mn-55 line, due to the Suhl-Nakamura interaction is observed, which suggests that the ferromagnetic metallic double exchange regions, at liquid helium temperatures, are at least 4 nm in size.</p

Nuclear magnetic resonance study of insulator-metal transitions in (Pr,Ca)MnO3

An NMR study of polycrystalline Pr0.5Ca0.5Mn1-xGaxO3 (x=0 and 0.03) and Pr0.67Ca0.33MnO3 at 3 K is presented. Zero-field spin-echo spectra of the Ga-doped compound consist of an overlapping Ga-69,Ga-71 signal at 74 MHz (hyperfine field of 5.3 T) and a Mn-55 double-exchange (DE) line at 375 MHz (35.5 T). Measurements in an applied field show a steplike increase in the DE line intensity, which corresponds to an increase of the amount of the ferromagnetic metallic phase. This coincides with a steplike feature in the bulk magnetization measurements. The effect is similar to that in the previous field-dependent Mn-55 NMR measurements of Pr0.67Ca0.33MnO3. The insulator - metal transition for Pr0.67Ca0.33MnO3, at ambient pressure, occurs at fields greater than 5 T; however, at 1.1 GPa, the DE line corresponding to the ferromagnetic metallic phase is already present at zero field.</p

An NMR study of Pr0.5Ca0.5Mn1-xGaxO3 (X=0 and 0.03)

An NMR study of polycrystalline Pr$\text{}_{0.5}$Ca$\text{}_{0.5}$Mn$\text{}_{1-x}$Ga$\text{}_{x}$O$\text{}_{3}$ (x=0 and 0.03) at 3 K is presented. Zero field spin-echo spectra of the Ga doped compound consist of an overlapping $\text{}^{69,71}$Ga signal at 74~MHz (hyperfine field of 5.3 T), a $\text{}^{55}$Mn double exchange line at 375 MHz (35.5 T) and a weak Mn$\text{}^{3+}$ signal between 400 and 550 MHz. Measurements in an applied field show a step-like increase in the double exchange line intensity, which corresponds to an increase in the amount of the ferromagnetic metallic phase. This coincides with a step-like feature in the bulk magnetization measurements. The effect is similar to that in the previous field dependent $\text{}^{55}$Mn NMR measurements of Pr$\text{}_{0.67}$Ca $\text{}_{0.33}$MnO$\text{}_{3}$. At the demagnetized and remanent state, a variation of spin- spin relaxation time, T$\text{}_{2}$, across the $\text{}^{55}$Mn line, due to the Suhl-Nakamura interaction is observed, which suggests that the ferromagnetic metallic double exchange regions, at liquid helium temperatures, are at least 4 nm in size