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The effect of hydrostatic pressure on antiferromagnetic ordering of Cr spins, magnetic compensation, and exotic spin switching in the single-crystal $\mathrm{GdCr}{\mathrm{O}}_{3}$ ferrimagnet is studied. The N\'eel temperature ${T}_{\mathrm{N}}=168\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ increases under pressure with the rate of 0.42 K/kbar, and the compensation temperature ${T}_{\mathrm{comp}}=144\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ at which the canted ferromagnetic moment of Cr spins and antiparallel polarized moment of Gd spins cancel each other also increases by 0.3 K/kbar. It was found that the spin switching temperature ${T}_{\mathrm{sw}}$, at which the ferromagnetic moment is reversed, noticeably increases under pressure, and the spin switching energy required for magnetization reversal reduces significantly because of a decrease in magnetic anisotropy. Due to this mechanism, the spin switching line, described in the $T$\ensuremath{-}$H$ diagram by a certain ratio of switching energy to canted ferromagnetic moment, is shifted under pressure towards higher temperatures. Thus, switching between two opposite spin configurations in the $\mathrm{GdCr}{\mathrm{O}}_{3}$ ferrimagnet can be controlled by both applied magnetic field and external pressure.

Magnetic and structural properties of CaMn1– x Re x O3 (0.02 ≤ x ≤ 0.1) have been investigated. Substitution of Re5+ ion for the Mn4+ site of 3 generates Mn3+ ions according to the chemical formula CaMn1–2 x 4+Mn x 3+Re x 5+O3, accompanied by an increase of lattice parameters and unit-cell volume with increasing ${x}$ . With increasing doping level $x$ , the magnetic ground state evolves from an antiferromagnetic (AFM) with a weak ferromagnetic (FM) component, for $x = 0.02 - 0.06$ , to the charge ordered ${C}$ -type AFM state at $x = 0.1$ . Spontaneous magnetization at $T = 10$ K increases quickly with increasing $x$ , approaches the maximum value of 3.5 emu/g for $x = 0.04$ , and then decreases rapidly to 0.2 emu/g for $x = 0.1$ . Anomalous negative magnetization (NM) for $x = 0.02$ has been observed in the zero-field-cooled and field-cooled (FC) magnetization below the magnetic transition temperature. Exchange bias (EB) effect, manifested by horizontal shift in the hysteresis loops of FC samples, has also been observed. This effect is very small for $x = 0.02$ , almost zeroes for 0.04, and monotonously increases with increasing $x$ . The EB appears due to low-temperature phase separation into FM clusters and charge-ordered AFM phases. The effect of hydrostatic pressure for all samples revealed a significant increase of the FM phase volume under pressure, linked to both suppression of NM in $x = 0.02$ sample and reduction of the EB effect in all samples.

An unusual exchange bias (EB) effect in single-crystalline $\mathrm{GdCr}{\mathrm{O}}_{3}$ compensated ferrimagnet (fM), composed of two antiferromagnetically coupled Gd and Cr sublattices, presenting two opposite ferromagnetic (FM) moments, is reported. It is shown that the temperature- or field-induced fast reversal of the net FM moment in $\mathrm{GdCr}{\mathrm{O}}_{3}$ may be identified as a switching between two opposite spin configurations, attendant with abrupt drop in Zeeman energy $\ensuremath{\approx}{k}_{\mathrm{B}}(7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ per formula unit. It was found that the FM moment reversal is exchange biased in the narrow temperature interval above the compensation temperature ${T}_{\mathrm{comp}}=144\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Namely, the EB field emerges and diverges upon approaching ${T}_{\mathrm{comp}}$ at temperatures $Tg{T}_{\mathrm{comp}}$ while unexpectedly it collapses to zero below ${T}_{\mathrm{comp}}$. This is in contrast to experimental results obtained for compensated fMs $R\mathrm{Fe}{\mathrm{O}}_{3}\phantom{\rule{4pt}{0ex}}(R=\mathrm{Nd}$, Sm, Er) orthoferrites showing EB in a narrow range, both above and below ${T}_{\mathrm{comp}}$. We suppose that breakdown of EB in $\mathrm{GdCr}{\mathrm{O}}_{3}$ may be linked to the lack of anisotropy of the spin-only Gd $S$-ion magnetic moment dominating below ${T}_{\mathrm{comp}}$.

Recent experiments showed magnetic moment reversal and pronounced exchange-bias (EB) effect in the vicinity of the compensation temperature ${T}_{\mathrm{comp}}$ of orthoferrites $R\mathrm{Fe}{\mathrm{O}}_{3}$ ($R=\mathrm{Nd}$, Sm, Er). Although different orthoferrites exhibit diverse $R$-Fe interactions, ${T}_{\mathrm{comp}}$ values, and spin-reorientation temperatures, the EB field in the like manner emerges and diverges upon approaching ${T}_{\mathrm{comp}}$ and changes its sign with crossing ${T}_{\mathrm{comp}}$. In order to explain these observations, a mean-field theory approach for the representative $\mathrm{ErFe}{\mathrm{O}}_{3}$ orthoferrite is proposed. The general case of two sublattices, antiferromagnet with exchange anisotropy and rare-earth--iron interactions, is considered. A small applied magnetic field appears to be a source of additional anisotropy, resulting from canting of sublattice moments. This anisotropy leads to an imbalance of free energy for two different types of magnetic domains, causing a spin jump near the ${T}_{\mathrm{comp}}$. The suggested approach allows reproduction of magnetization reversal and main features of the coercive and exchange-bias fields observed in $\mathrm{ErFe}{\mathrm{O}}_{3}$.

Magnetic properties of bulk polycrystalline Mn-doped SrRu 1− x Mn x O 3 perovskite, at doping range 0.2≤ x ≤0.3, were studied by both magnetization and ac-susceptibility measurements. It was found that the exchange bias (EB) effect emerges with increasing Mn doping in SrRu 1− x Mn x O 3 at x ≈0.25, following the ferromagnetic (FM) to antiferromagnetic (AFM) phase transition. This transition is accompanied with the change in structure symmetry and then the EB field, H EB , increases significantly in doping range 0.25 x ≤0.3. The EB effect was verified by both cooling magnetic field, H cool , dependence of the H EB and training effect. A markedly nonmonotonic H EB vs. H cool dependence with maximum at around 40 kOe was found, resembling the behavior of phase-separated EB systems. Moreover, a clear analogy with behavior of classic EB system of Pr 1/3 Ca 2/3 MnO 3 was noticed, strongly suggesting that the EB effect in SrRu 1− x Mn x O 3 originates from exchange interactions at the interface of nanoscale FM clusters (size of ~1.6 nm at x =0.3) coe x isting together with dominant AFM phase at the boundary of the first-order FM/AFM transition. The training effect observed is well understandable within the spin-configuration relaxation model and indicates important contribution to the EB behavior from the AFM domains rearrangement at the interface.

The exchange bias (EB) effect and an appearance of the Griffiths phase (GP) were found in half-doped cobaltite $\mathrm{G}{\mathrm{d}}_{0.5}\mathrm{S}{\mathrm{r}}_{0.5}\mathrm{Co}{\mathrm{O}}_{3\ensuremath{-}\ensuremath{\delta}}$ exhibiting a significant quenched disorder due to the ion size mismatch between Sr and Gd. The disorder weakens the ferromagnetic (FM) interactions between Co ions, leading to low Curie temperature ${T}_{C}=90\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and to a highly nonhomogenous magnetic state above ${T}_{C}$. A clear GP behavior was detected in the temperature range between ${T}_{C}$ and the Griffiths temperature ${T}_{G}=225\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Moreover, this GP demonstrates a unique feature; namely, the appreciable EB effect exists concomitantly within the GP, suggesting coexisting FM and antiferromagnetic nanocluster phases. It was found that the EB exists in $\mathrm{G}{\mathrm{d}}_{0.5}\mathrm{S}{\mathrm{r}}_{0.5}\mathrm{Co}{\mathrm{O}}_{3\ensuremath{-}\ensuremath{\delta}}$ for the entire temperature range below ${T}_{G}=225\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, in contrast to the limited low-temperature EB observed so far in perovskite cobaltites. The EB has a different nature in the FM cluster phase below ${T}_{C}$ and in the GP in temperature interval ${T}_{C}lTl{T}_{G}$. The cooling field effect on EB was examined in the GP, and the size of FM clusters was determined to be equal to 6.5 nm.

The unconventional exchange-bias (EB) effect in single crystals of $R\mathrm{Fe}{\mathrm{O}}_{3}(R=\mathrm{Nd},\phantom{\rule{0.28em}{0ex}}\mathrm{Sm})$ compensated ferrimagnets (fMs), composed of two antiferromagnetically (AFM) coupled $R$ and Fe sublattices with opposite ferromagnetic (FM) moments, exhibiting the FM moment reversal via a fast spin switching is reported. In ${\mathrm{NdFeO}}_{3}$, the EB anisotropy field emerges and diverges upon approaching the compensation temperature ${T}_{\mathrm{comp}}^{\mathrm{Nd}}=9.2\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, and changes sign with crossing ${T}_{\mathrm{comp}}^{\mathrm{Nd}}$, in similarity to the behavior observed recently in ${\mathrm{ErFeO}}_{3}$. In contrast, ${\mathrm{SmFeO}}_{3}$ exhibits a substantial EB, not only at its ${T}_{\mathrm{comp}}^{\mathrm{Sm}}=4.8\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, but also at higher temperatures up to 100 K, and the EB changes its sign with increasing cooling field. It is shown that in all known $R{\mathrm{FeO}}_{3}$ ($R=\mathrm{Nd},\phantom{\rule{0.28em}{0ex}}\mathrm{Sm},\phantom{\rule{0.28em}{0ex}}\mathrm{Er}$) compensated fMs the field-induced FM moment reversal is similarly exchange biased near ${T}_{\mathrm{comp}}$.

The exchange-bias (EB) effect with sign reversal was found in $\mathrm{LuF}{\mathrm{e}}_{0.5}\mathrm{C}{\mathrm{r}}_{0.5}{\mathrm{O}}_{3}$ ferrite-chromite, which is a weak ferrimagnet below ${T}_{\mathrm{N}}=265\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, exhibiting antiparallel orientation of the ferromagnetic (FM) moments of the Fe and Cr sublattices due to opposite sign of the Fe-Cr Dzyaloshinskii vector, as compared to that of the Fe-Fe and Cr-Cr. The weak FM moments of the studied compound compensate each other at temperature ${T}_{\mathrm{comp}}=230\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, leading to the net magnetic moment reversal and to observed negative magnetization, at moderate applied fields, below ${T}_{\mathrm{comp}}$. Both vertical and horizontal shifts from the origin were gotten in the field-cooled magnetization hysteresis loops. The EB sign was found to be positive below ${T}_{\mathrm{comp}}$ and negative above ${T}_{\mathrm{comp}}$, with nonmonotonic dependence on cooling field ${H}_{\mathrm{cool}}$. It sharply increases at small values of magnetic fields up to ${H}_{\mathrm{cool}}\ensuremath{\sim}1\phantom{\rule{0.16em}{0ex}}\mathrm{kOe}$, then remains almost unchanged in the range 1--30 kOe and strongly decreases with further increase of ${H}_{\mathrm{cool}}$. This unusual behavior results from the competition of various Dzyaloshinskii-Moriya interactions between $\mathrm{F}{\mathrm{e}}^{3+}$ and $\mathrm{C}{\mathrm{r}}^{3+}$ ions.

The effect of hydrostatic pressure on complex magnetic phase diagram of $\mathrm{LuF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}$ has been investigated by various magnetic measurements in the range of 0--12 kbar. The temperature of the ferrimagnetic (fM) transition (${T}_{\mathrm{N}}\ensuremath{\approx}245\phantom{\rule{0.16em}{0ex}}\mathrm{K}$) practically does not change with increasing pressure, while the temperature of the appearance of mixed fM and antiferromagnetic (AFM) state at $\ensuremath{\sim}\phantom{\rule{0.16em}{0ex}}200\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ increases with the rate $d{T}_{\mathrm{C}}/dP\ensuremath{\approx}0.8\phantom{\rule{0.16em}{0ex}}\mathrm{K}/\mathrm{kbar}$. Moreover, an applied pressure suppresses the magnetization, enhances the field of metamagnetic transition, and extends the range of existence of mixed fM and AFM state. Suppression of the ordered magnetic moment under pressure induces a transition from a counterclockwise (CCW) thermal hysteresis below $T\ensuremath{\approx}220\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ to a clockwise (CW) thermal hysteresis in a magnetic field $H=1\phantom{\rule{0.16em}{0ex}}\mathrm{kOe}$. Nevertheless, field induced metamagnetic transition from mixed fM and AFM state to fM state results in a narrowing of the temperature range of thermal hysteresis and in restoring of CCW type of thermal hysteresis. As a consequence of metamagnetic transition, the thermal hysteresis completed at $H=10\phantom{\rule{0.16em}{0ex}}\mathrm{kOe}$ remains one of the CCW type under applied pressure.

An exchange bias (EB) effect was observed in mixed valent $\mathrm{L}{\mathrm{a}}_{x}\mathrm{B}{\mathrm{a}}_{1\ensuremath{-}x}\mathrm{Fe}{\mathrm{O}}_{3}$ ($x=0.125$, 0.25, 0.33) perovskites exhibiting the antiferromagnetic (AFM) helical order among $\mathrm{F}{\mathrm{e}}^{4+}$ ions coexisting with the ferromagnetic (FM) cluster phase in the ground state. The $\mathrm{L}{\mathrm{a}}^{3+}$ ions for $\mathrm{B}{\mathrm{a}}^{2+}$ site substitution, associated with increase in number of the AFM coupled $\mathrm{F}{\mathrm{e}}^{3+}$ - $\mathrm{F}{\mathrm{e}}^{4+}$ pairs as well as some $\mathrm{F}{\mathrm{e}}^{3+}$ - $\mathrm{F}{\mathrm{e}}^{3+}$ pairs, leads to strengthening of the AFM phase and consequently to the alteration of the EB characteristics, which depend on level of the La doping $x$. At low doping $x\ensuremath{\le}0.25$, an abnormal dependence of the EB field, ${H}_{\mathrm{EB}}$, on the cooling field, ${H}_{\mathrm{cool}}$, was found. The ${H}_{\mathrm{EB}}$ increases rapidly with increasing cooling field at low ${H}_{\mathrm{cool}}$, but it falls suddenly at cooling fields higher than 20 kOe, reducing by an order of magnitude at 90 kOe. The suppression of EB is caused by the field-induced increased volume of the FM phase, due to the transformation of the AFM helical spin structure into the FM one. Thus, low-doped $\mathrm{L}{\mathrm{a}}_{x}\mathrm{B}{\mathrm{a}}_{1\ensuremath{-}x}\mathrm{Fe}{\mathrm{O}}_{3}$ demonstrates a competition of two alternate cooling-field-induced effects, one of which leads to the EB anisotropy and another one to the enhanced ferromagnetism. In contrast, the $x=0.33$ sample, having a strong AFM constituent, shows no field-induced FM and no drop in the EB field. Accordingly, the ${H}_{\mathrm{EB}}$ vs ${H}_{\mathrm{cool}}$ dependence was found to be well explained in the framework of a model describing phase-separated AFM-FM systems, namely, the model assuming isolated FM clusters of size \ensuremath{\sim}4 nm embedded in the AFM matrix.

Non-equilibrium magnetic properties of the near half-doped Sm 0.43 Ca 0.57 MnO 3 nanoparticles with an average size as small as 15 nm have been investigated by measuring temperature dependence of zero field cooled (ZFC) magnetization, ac-susceptibility, time dependence of ZFC magnetization, relaxation of the remanent magnetization, and memory effects in ZFC magnetization. For the studied particles, charge ordering, characteristic for the bulk, is gradually suppressed with decreasing particle size and fully disappears in 15 nm particles, while the Neel temperature decreases slightly from 73 K for 60 nm to 58 K for 15 nm particles. It was found that dipolar interaction between 15 nm nanoparticles is enough to leads to the formation of a superspin glass state. Characteristic features of superspin glass state, such as aging and memory effects have been observed in 15 nm samples. In a difference to atomic spin glasses, no strong rejuvenation of magnetization has been observed at low temperatures.

Size dependence of magnetic properties of Sm0.43Ca0.57MnO3 nanoparticles with average size of 15–60 nm has been investigated. Charge ordering, characteristic for the bulk form of this material, was found to be gradually suppressed with decreasing particle size and fully disappearing in 15 nm nanoparticles. Onsets of ferromagnetic contributions to the magnetization appear below 90 K, independently on the particle size, while spontaneous magnetization at 10 K increases with decreasing particle size. Magnetic hysteresis loops exhibit size dependent exchange bias effect manifested by horizontal HEB and vertical MEB shifts, appearing after field cooling. Variation of HEB and MEB shows opposite size dependences; HEB decreases while MEB increases with decreasing particle size. For large 60 nm particles, HEB decreases monotonously with increasing temperature, while for the smallest 15 nm particles it shows surprising nonmonotonic temperature dependence. Size and temperature dependences are discussed in terms of m...

An exchange-bias (EB) effect observed in single crystal $\mathrm{ErFe}{\mathrm{O}}_{3}$ compensated ferrimagnet, exhibiting the EB field ${H}_{\mathrm{EB}}$ increasing and diverging upon approaching compensation temperature ${T}_{\mathrm{comp}}=45\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, and changing sign with crossing ${T}_{\mathrm{comp}}$, is reported. The EB sign may be changed to the opposite one by varying the field-cooling protocol, depending on whether ${T}_{\mathrm{comp}}$ is crossed with decreasing or increasing temperature. Namely, a different EB sign with the same $|{H}_{\mathrm{EB}}|$ and coercive field ${H}_{\mathrm{C}}$ values is obtained approaching a given $T$ with increasing and decreasing temperature and the ${H}_{\mathrm{EB}}(T)$ dependence completed in one way is a mirror image of that completed in another way.

Structural and magnetic properties of La0.2Ca0.8MnO3 nanoparticles with average size of 15-37 nm, prepared by the glycine-nitrate method, have been studied. Synchrotron experiments performed in the temperature range of 80-300 K have shown that a structural transition from room temperature orthorhombic Pnma to monoclinic P2(1)/m space group, associated with orbital ordering, occurs below 200 K in the studied particles. This transition observed for the largest particles of 37 nm is very close to that of bulk, as seen by similar temperature variation of lattice parameters and orthorhombic strain. The transition is highly suppressed for smaller 15 nm particles. Horizontal and vertical shifts of magnetic hysteresis loops (M(Shift) and H(EB)), displayed in a field cooled process, indicate size dependent exchange bias effect. It is also shown that M(shift) and H(EB), as well as the remanent magnetization M(r) and coercive field H(c) at low temperatures, exhibit a non-monotonic size dependence for particles around 23 nm. These effects may be attributed to the changes in uncompensated spins at the surface, anisotropy or alternatively to a transition from a multi-domain to the single domain state.

Magnetic properties of compacted Sm0.8Ca0.2MnO3 (SCMO) particles with average particle size of 23-100 nm, prepared by the glycine-nitrate method, have been investigated. It was found that the relative volume of the ferromagnetic phase decreases with decreasing particle size. Curves of field cooled and zero filed cooled magnetization (M(ZFC)) exhibit a bifurcation just below the Curie temperature (T(c) approximately 55-64 K) for all particles studied. The field dependence of M(ZFC) peak follows de Almeida-Thouless line. Both features are characteristic of spin-glasses (SG). Measurements of ac-susceptibility in the temperature range 5-300 K and the frequency range f = 10 Hz-10 kHz show a sharp peak for both real and imaginary components in the vicinity of T(c), apparently attributed to the Hopkinson effect. A second small peak is seemingly associated with antiferromagnetic or ferrimagnetic ordering. Though, for smaller particles both peaks depend on frequency, no shift to higher temperatures with increasing f, characteristic for SG systems, was observed. The dissimilarity in magnetic properties and dynamic characteristics observed for SCMO and for La0.8Ca0.2MnO3 nanoparticles is discussed, taking into account a difference in the width of the band and the strength of double exchange and interparticle interactions.

We report the structural and magnetic properties of La0.2Ca0.8MnO3 nanoparticles synthesized by a chemical route, having an average diameter of 15 nm. Synchrotron experiments performed in the temperature range 80−300 K have shown that below 200 K a structural transition from room temperature orthorhombic Pnma to monoclinic P21/m space group, associated with orbital ordering, survives in studied particles, although this transition is highly suppressed in comparison with that of the bulk. The magnetization of these particles exhibits the appearance of a ferromagnetic contribution from the shell at T > 200 K, antiferromagnetic ordering within the particle core at TN ∼ 140 K, and the emergence of another ferromagnetic contribution at T < 100 K. The latter appears as a result of spin canting within the antiferromagnetic core or is developed at some interfaces inside the nanoparticles. Considerable horizontal (HEB) and vertical (MShift) shifts of the magnetization hysteresis loops are observed after field cooli...

Transport and magnetic properties of LaMnO3+δ nanoparticles with average size of 18 nm have been investigated. The ensemble of nanoparticles exhibits a paramagnetic to ferromagnetic (FM) transition at TC∼246 K, while the spontaneous magnetization disappears at T≈270 K. It was found that the blocking temperature lies slightly below TC. The temperature dependence of the resistivity shows a metal–insulator transition at T≈192 K and low-temperature upturn at T

Magnetic properties of nanocrystalline LaMnO 3 + δ manganites with particle sizes of 20 (LMO20), 25 (LMO25), and 30 nm (LMO30), prepared by the citrate method, have been investigated. All nanoparticles exhibit paramagnetic to ferromagnetic transition (PFT) at T C > 200 K . It was found that the relative volume of the ferromagnetic phase increases with increasing particle size and approaches a value of about 93% for LMO30. Ac susceptibility of LMO20 sample exhibits strong frequency dependence below T C , whereas for LMO30 sample only weak frequency dependence was observed. The magnetization of LMO30 sample exhibits a PFT of second order. It was found that an applied pressure enhances T C of LaMnO 3 + δ particles with a pressure coefficient of d T C / d P ≈ 1.4 – 1.9 K / kbar for all samples. Peculiar magnetic memory and negative magnetization effects observed for LMO20 sample are discussed.

International audience; Magnetic properties of antiferromagnetic (AFM) electron doped manganite Sm0.1Ca0.7Sr0.2MnO3 have been investigated, focusing mainly on the exchange bias (EB) effect and associated training effect. The studied compound exhibits the ground state with heterogeneous spin configuration, consisting of the C-type antiferromagnetic phase with the Néel temperature TN-C ≈ 120 K, the G-AFM phase with the Néel temperature TN-G ≈ 60 K, and ferromagnetic-like phase with a very weak spontaneous magnetic moment. Measurements of hysteresis loops have shown that the exchange bias field monotonously decreases with increasing temperature and vanishes above 40 K, while the coercivity disappears only above 70 K. The temperature variation of the exchange bias field has been successfully described by an exponential decay form. The stability of EB has been evaluated in the studies of the training effect, which has been discussed in the frame of the spin relaxation model, elucidating the important role of the AFM domain rearrangement at the interface. The complex phase separation and possible contributions from different interfaces between coexisting magnetic phases to the EB effect have also been discussed. © 2016 Elsevier B.V.

Magnetic properties of Pr0.5Ca0.5Mn1−xCrxO3 (0.015⩽x⩽0.5) samples were investigated under pressures up to 11 kbar. For x=0.015 and 0.03 samples, an applied pressure enhances significantly the Curie temperature (dTC/dP∼2 K/kbar), enhances the ferromagnetic phase volume below TC, and narrows appreciably the hysteresis in the vicinity of TC. For x=0.2 and 0.5 samples, pressure does not affect practically the magnetic transition temperature, but reduces noticeably the magnetization in a wide temperature range. Observed phenomena for x=0.015 and 0.03 samples are related to the interfacial elastic energy at the interface of different magnetic phases and to the suppression of the Jahn–Teller distortions under pressure. For higher doped samples, pressure possibly increases antiferromagnetic interactions between Cr3+ and Mn4+ ions.

Magnetic properties of polycrystalline Sm0.1Ca0.9−ySryMnO3 (y = 0–0.3) samples have been investigated in the temperature range 5–250 K, magnetic fields up to 16 kOe and under hydrostatic pressures up to 11 kbar. The studies involved sequential measurements of zero field cooled (ZFC) magnetization and measurements of magnetization upon cooling in the same magnetic field (FCC). The low-doped group (y = 0–0.1) exhibits magnetic phase separation below TN≈TC≈100–110 K, consisting of ferromagnetic (FM) clusters embedded in an antiferromagnetic (AFM) G-type matrix. Magnetization and ac-susceptibility measurements of this group of materials indicate features reminiscent of a cluster glass-like state, below TC. It was found that the volume fraction of the FM phase at 10 K decreases with increasing y from 28% for Sm0.1Ca0.9MnO3 to 18% for Sm0.1Ca0.8Sr0.1MnO3. It was found that an applied pressure enhances TC with a pressure coefficient of dTC/dP≈0.4–0.5 K kbar−1. The low-temperature magnetization at this doping range (y = 0–0.1) depends on pressure only slightly, except for the case of Sm0.1Ca0.8Sr0.1MnO3, where an applied pressure enhances the FM phase volume considerably. Samples with y = 0.2 and 0.3 exhibit a heterogeneous spin configuration in their ground state, consisting of a C-AFM phase and a G-AFM phase with a very weak FM moment. The temperature of transition from the paramagnetic to the C-AFM state is almost insensitive to applied pressure, whereas the lower transition temperature to the G-AFM state increases slightly under pressure. It was found also that an applied pressure considerably reduces the FM correlations in the paramagnetic phase as well as the FM component of the G-AFM state.

We present the study of magnetic and transport properties of Pb(1-x-y-z)Mn(x)Sn(y)Eu(z)Te. AC magnetic susceptibility measurements as well as transport characterization were performed. The obtained results indicate that the presence of two types of magnetic ions influences magnetic properties of investigated IV-VI semimagnetic semiconductor. A qualitative analysis and possible mechanisms of the substantial dependence of the Curie temperature on the Eu content are presented. The most likely reason of the observed Curie temperature behaviour is a strong dependence of the location of a heavy mass Sigma band upon the alloy composition. The theoretical calculations in frame of simple models confirm this point.

The magnetic properties of La0.70Sr0.30MnO2.85 anion-deficient manganite are studied experimentally under hydrostatic pressure. The results show that, in the whole pressure range under investigation (0–1 GPa), the sample is a spin glass with a smeared phase transition to the paramagnetic state. It is found that the spin glass state arises from the frustration of the exchange coupling of the ferromagnetic clusters embedded in the antiferromagnetic matrix. The fraction of the sample volume occupied by the ferromagnetic phase is found to be V fer ∼ 13%. Under hydrostatic pressure, the freezing temperature T f of the magnetic moments of the ferromagnetic clusters increases at a rate of 4.30 K/GPa and the magnetic ordering temperature T MO increases at a rate of 12.90 K/GPa. In addition, the ferromagnetic part of the sample increases by ΔV fer ∼ 5%. The enhancement of the ferromagnetic properties of La0.70Sr0.30MnO2.85 anion-deficient manganite under hydrostatic pressure is explained by the redistribution of oxygen vacancies and a decrease in the unit-cell parameters.

Magnetic and transport properties of polycrystalline CaMn 1− x Ru x O 3 ( x = 0 – 0.4 ) perovskites were investigated under pressures up to 12 kbar. It was found that an applied pressure suppresses ferromagnetism and increases resistivity. The results are discussed in the context of phase separation and valence effects.

Measurements of electrical resistance and magnetization of an La 0.8 Ca 0.2 MnO 3 single crystal were carried out at temperatures below and above the Curie temperature, T C =183.5±1 K. The effect of applied hydrostatic pressure P and magnetic field H on the magnetization and the resistive properties were also investigated. It was found that the pressure coefficient of the Curie temperature is rather small d T C /d P ≈0.3 K/kbar. At low temperatures a positive magnetoresistance was found. A nonlinear dependence of resistivity as a function of DC current was revealed. The results are interpreted in the frame of phase separation scenario.

The effect of lanthanum deficiency on structural, magnetic, transport, and electron magnetic resonance (EMR) properties has been studied in a series of La1−xMnO3 (x = 0.01, 0.05, 0.11, 0.13) single crystals. The x-ray diffraction study results for the crystals were found to be compatible with a single phase of orthorhombic symmetry. The magnetization curves exhibit weak ferromagnetism for all samples below 138 K. It was found that both the spontaneous magnetization and the coercive field increase linearly with x. The pressure coefficient dTN/dP decreases linearly with self-doping, from a value of 0.68 K kbar−1 for La0.99MnO3 to 0.33 K kbar−1 for La0.87MnO3. The resistivity of low-doped La0.99MnO3 crystal is of semiconducting character, while that of La0.87MnO3 depends weakly on temperature between 180 and 210 K. It was found that the magnetic and transport properties of the self-doped compounds may be attributed to a phase separation involving an antiferromagnetic matrix and ferromagnetic clusters. The latter phases as well as their paramagnetic precursors have been directly observed by means of EMR.

The magnetic and transport properties of La1−xMn1+xO3 manganites with excess manganese are studied. It is shown that magnetic and charge ordering heavily depends on the superstoichiometric manganese content, magnetic field, and pressure. The magnetoresistive effect (MRE) is enhanced as the manganese concentration increases. In addition to the paramagnet-ferromagnet transition, the temperature dependences of the magnetization exhibit anomalies at low temperatures in samples with x=0.1–0.4. The magnetization decreases at T

International audience; The exchange bias effect in CaMn0.9Nb0.1O3 has been investigated. It was found that both vertical and horizontal shifts in magnetic hysteresis loop of field cooled sample decrease monotonously with increasing temperature and vanish above 70 K, while the coercivity disappears only above 90 K, upon approaching the Néel temperature. An exponential decay successfully describes variation of the shifts with temperature. The exchange bias phenomenon is in general attributed to low-temperature phase separation into ferromagnetic clusters immersed in the G-type or C-type antiferromagnetic matrix and the resulting appearance of interfaces between coexisting different magnetic phases. Our results indicate that the exchange bias effect in CaMn0.9Nb0.1O3 may be induced, at least partially, by Dzyaloshinsky-Moriya interactions. Measurements of hysteresis loops at various cooling fields from the range -90 < H < 90 kOe show that magnetization at magnetic field H > 20 kOe exhibits a nonlinear increase and a sort of metamagnetic transition that appears to be responsible for a complete suppression of the exchange bias effect in CaMn0.9Nb0.1O3 at high magnetic field. © 2015 Elsevier B.V. All rights reserved.

International audience; Magnetic investigations, focused on the uncommon behavior of the exchange bias (EB) effect, have been performed for basically antiferromagnetic (AFM) electron doped manganite Sm0.1Ca0.6Sr0.3MnO3. The studied system in the ground state exhibits a heterogeneous spin configuration consisting of the C-type antiferromagnetic phase with the Néel temperature TN-C ≈ 150 K, the G-type AFM phase with the Néel temperature TN-G ≈ 70 K, and a FM-like phase with very weak spontaneous magnetic moment. The phase separation, into two different AFM phases and a FM-like phase at the temperatures below TN-G, leads to unusual magnetic properties, such as narrowing of magnetic hysteresis loops in field cooling process, unconventional EB effect associated with spontaneous magnetization at temperatures below TN-C, strong magnetic field dependence of the negative exchange bias at fields below 100 Oe turning into practically field independent one for fields above 0.5 kOe, significant shift of EB with temperature with a change of the sign from negative at 10 K to positive above 40 K. The atypical magnetic properties are discussed and related to two different interfaces appearing between coexisting magnetic phases. © 2014 Elsevier B.V. All rights reserved.

In this paper, we report on the effect of excess manganese on the magnetic properties of the (La0.7Ca0.3)1−xMn1+xO3 perovskites. All samples display a colossal magnetoresistance effect which becomes considerably enhanced with increasing manganese content. The magnetic behaviour of manganites studied was shown to depend strongly on the values of manganese doping and applied magnetic field. For the samples with x=0.1 and 0.2, in addition to an anomaly connected with paramagnet–ferromagnet transition, there are anomalies in the field-cooled (FC) and zero-field-cooled (ZFC) magnetization at low temperatures. In low magnetic fields (H 200 Oe, a jump upwards takes place in the MFC(T) and MZFC(T) curves at the same temperature. A low-temperature anomaly in AC susceptibility also indicates a change in magnetic ordered state. From M(T,H) and χ(T) dependencies, one can assume the existence of regions with different magnetic order at T

Investigations are performed of the crystal structure and magnetic and electromagnetic properties of single crystals (0.23 ≤x≤0.34) and polycrystals (0 ≤x ≤0.50) of an Nd1−x BaxMnO3−δ system of solid solutions. It is found that, for samples prepared in the air, the maximal Curie temperature (T C ) does not exceed 150 K, while, in the case of polycrystalline samples in the concentration range of 0.34 ≤x ≤0.50, prepared in a reducing medium (a gaseous mixture of argon and carbon monoxide), T C increases to 320 K. As a result of the reducing medium effect on the compositions, the type of the magnetic phase transition to the paramagnetic state changes from the first to second order. The electrical resistivity of reduced polycrystalline samples (0.34≤x ≤0.50) decreases in magnitude and correlates with the behavior of magnetization. Both series of samples, prepared both in the air and in a reducing medium, exhibit a transition from the metal to dielectric state at a temperature below T C . The temperature and field dependences of magnetization for the stoichiometric polycrystalline com-position of Nd0.50Ba0.50MnO3 are measured under conditions of hydrostatic pressure. It is demonstrated that the hydrostatic pressure induces in Nd0.50Ba0.50MnO3 the transition from the antiferromagnetic to ferromagnetic state. Based on the measurement results, hypothetical magnetic phase diagrams are constructed for the system of solid solutions being treated, depending on the concentration of barium and the method of preparation. It is found that no T TC increase is observed in single crystals (0.23≤x≤0.34) such as is observed in polycrystals. It is assumed that the abrupt increase in T C of polycrystalline samples prepared in a reducing medium is a result of the emergence of extended defects and microstresses in the crystal lattice.

Magnetization, electrical resistivity and magnetoresistance of Pr 0.50 Ba 0.50 MnO 3− δ manganites with perovskite structure have been investigated as a function of preparation conditions. It was found that the as-prepared samples (prepared in air) show T C =110 K (first order phase transition), whereas for those annealed in flowing argon the T C value increases up to 340 K without change of cubic symmetry (second order phase transition). Ferromagnet–paramagnet transition is accompanied by both a metal–insulator transition and a magnetoresistance peak. The X-ray study has revealed that the samples annealed in argon have broad peaks apparently due to microstrains and crystal structure defects. The argon-treated samples improve the magnetization after subsequent annealing in air at T ⩽1000°C. T C of argon-treated samples is stable with respect to annealing in air up to 1300°C where it becomes again 110 K. In contrast, a treatment in vacuum destroys the ferromagnetic order. Auger-spectroscopy has not revealed any additional ions except Pr, Ba, Mn and O for all the samples. External pressure enhances the Curie point of the sample prepared in air at a rate of 43 K/GPa. We have observed that the samples Pr 1− x Ba x MnO 3− δ , x⩾ 0.30, exhibited the above-mentioned effect of increasing T C after treatment in flowing argon without changes of the phase state, whereas the samples x T C after argon treatment is supposed to result from microstrains and crystal structure defects in the sample.

The investigation of Zn substitution in MgB2 polycrystalline samples shows that about 0.1 Zn can be substituted in the structure of Mg deficient samples while it can not be substituted in stoichiometric MgB2. As a result of the isovalent Zn substitution into the Mg position of Mg deficient samples the a and c lattice constants increase by about 0.17% and 0.2% respectively. Susceptibility measurements show a slight lowering of Tc by about 0.5 K for 0.05 Zn, which decreases to 0.2 K for 0.1 Zn substitution. Investigation of the pressure derivative of Tc shows dp/dTc = -0.15 K/kbar independent of Zn content. Substitution of Cu leads to multiphase samples without any changes of lattice constants, which indicates that Cu does not enter the structure of MgB2. The Cu substitution broadens the superconducting transition considerably, while the onset remains unchanged., Comment: 13 pages, 5 figures

Strongly underdoped NdBa2Cu3O6.67 ceramics is known to become superconducting under pressure only. The appearance of superconductivity in the sample originates from the oxygen ordering process, whereas its disappearance, after pressure release, comes from oxygen disordering. The time evolution of the a, b, and c lattice parameters in the relaxation process which occurs after pressure release from 1.3 GPa was studied by x-ray diffraction at two temperatures of 26 and 15 °C. The anisotropic expansion of the unit cell with different time dependence for each parameter was found at both temperatures. The largest change was observed along the a axis, which increased by 0.4%, while the b axis contracted by 0.08% and the c axis increased by 0.05% only. The corresponding orthorhombic strain b2a was reduced by 45%, while the unit-cell volume increased by about 0.4%. The rate of the structural relaxation process depends strongly on temperature. An increase in the relaxation time constant t ~from t’0.67 h to t’1.75 h! was observed with lowering temperature, as expected for oxygen motion with an activation energy of 0.91 eV. The experimental results are evidence that the disappearance of superconductivity after pressure release is related to the shortening of Cu-O chains due to O~1!!O~5! oxygen hopping, causing the hole transfer from CuO2 planes. The possible mechanisms of specific changes in the basal plane are discussed. We report also related results obtained for a more underdoped NdBa2Cu3O6.64 sample, which exhibits no superconductivity under the same pressure. The change in symmetry, from orthorhombic to tetragonal, in the disordering process occurring after pressure release at constant temperature, was observed for a 123 sample with fixed oxygen content.

Disappearance of superconductivity correlated with an increase of the unit cell volume, V cell , as a result of the oxygen disordering process caused by the pressure release was observed for NdBa 2 Cu 3 O 6.67 in both magnetic and X-ray measurements. Correlation between changes of T c and V cell under pressure is well described by a simple model based on the O(5)→O(1) transition in the CuO x planes. It was found that due to the oxygen ordering the compressibility of NdBa 2 Cu 3 O 6.67 increases with time by 30%. Superconductivity occurs at pressure p c =0.21 GPa. The T c ( p ) dependence is a nonlinear function of an applied pressure. The d T c /d p reaches value of 80 K/GPa near p c . Time asymmetry in the processes of oxygen ordering and disordering for both NdBa 2 Cu 3 O 6.67 and YBa 2 Cu 3 O 6.38 was found.

The data of low-temperature magnetic measurements of the monoclinic KDy(WO 4 ) 2 crystal are used to calculate the exchange and dipole–dipole interactions energy. The last are used for the determination of the magnetic structure of the ground state.

Magnetic and structural properties of nanocrystalline LaCoO 3 with particle size ranging from 25 to 38 nm, prepared by the citrate method, were investigated. All nanoparticles exhibit ferromagnetism below T C ≈ 85 K. It was found that the unit-cell volume increases monotonically with decreasing particle size and ferromagnetic (FM) moment increases simultaneously with lattice expansion, whereas T C remains nearly unchanged. It appears that both magnetic and structural properties of LaCoO 3 nanoparticles are size-dependent due to the surface effect. On the other hand, an applied pressure suppresses strongly the FM phase leading to its disappearance at ∼11 kbar. Remarkably, the T C does not change visibly under pressure. Our data reveal that the ferromagnetism in LaCoO 3 nanoparticles, likely related to the intermediate-spin (IS) Co 3+ state, is simply controlled by the unit-cell volume. Within this scenario, the FM coupled IS states appear/disappear with expanding/compressing the lattice and/or Co–O bonds.

The pressure controlled oxygen reordering processes in REBa 2 Cu 3 O 6+x (RE=Y,Nd,La) causing the continous charge transfer between the CuO x and CuO 2 planes were investigated. The charge transfer results in the time evolution of superconductivity. A strong acceleration of ordering and disordering processes was found when the RE-ion size increases from Y to La. Pressure induced semiconductor-superconductor transition in LaBa 2 Cu 3 O 6+x resulted from the oxygen ordering is reported for the first time.

The relaxation of the superconducting transition temperature T c in YBa2Cu3O6.38 is investigated with increasing oxygen order in the CuOx plane under 1 GPa pressure and with decreasing oxygen order after the pressure is relieved. It is established that the oxygen disordering process is more rapid than the pressure-induced ordering process: The ratio of the relaxation times of T c in these processes τ ord/τ disord≈5. This behavior could be caused by different mechanisms of the pressure-induced increase in the Cu-O chain length and decrease of this length after pressure relief.

The appearance of superconductivity and relaxation of the transition temperature to its equilibrium value Tc≈30 K over the course of five days have been observed in a tetragonal sample of NdBa2Cu3O6.67 under 1 GPa pressure. The time dependence Tc(t) correlates with a decrease of the room-temperature electrical resistance R(t). The superconducting phase disappears 1.3 h after the pressure is removed. This behavior is explained by a redistribution of charge as a result of pressure-induced oxygen reordering in the CuOx planes. A large effect of oxygen ordering on the transition temperature under pressure has been observed near the metal-insulator transition (the largest of all those measured in the 1-2-3 system), along with a nonlinear temperature dependence of Tc.

For the first time the insulator-superconductor transition in tetragonal NdBa2Cu3O6.67 ceramics has been induced by pressure. The superconductivity (with Tc = 12 K) was first observed after 3.6 h exposure of the sample to a pressure of 1 GPa at room temperature. The relaxation of Tc to the equilibrium value of about 30 K under pressure of 1 GPa was observed during 5 days. After the pressure was released the superconductivity disappeared within 1.3 h. The observed effects are interpreted as being the direct consequence of charge redistribution between CuO2 planes and CuO chains as a result of the oxygen ordering processes under pressure.

The pressure effect on exchange bias (EB) and coercive fields, ${H}_{\mathrm{E}}$ and ${H}_{\mathrm{C}}$, in phase-separated ferromagnetic/antiferromagnetic (FM/AFM) CaMn${}_{1\ensuremath{-}x}$Ru${}_{x}$O${}_{3}$ manganites with 0.06 \ensuremath{\le} $x$ \ensuremath{\le} 0.15 was studied by magnetization measurements performed in the temperature range 10--200 K and under hydrostatic pressure up to 11 kbar. Both ${H}_{\mathrm{E}}$ and ${H}_{\mathrm{C}}$ exhibit intriguing dependence on Ru doping and on applied pressure. It was found that ${H}_{\mathrm{E}}$ is apparent only at $x$ 0.1 and decreases progressively with increasing doping, while ${H}_{\mathrm{C}}$ depends nonmonotonically on Ru content, reaching a maximum at around $x$ \ensuremath{\sim} 0.09. The ${H}_{\mathrm{E}}$ was found to increase strongly under applied pressure within doping range 0.06 \ensuremath{\le} $x$ \ensuremath{\le} 0.1, while ${H}_{\mathrm{C}}$ exhibits irregular behavior, namely, increases with increasing pressure for $x$ $=$ 0.15, changes nonmonotonically for $x$ $=$ 0.1, decreases for $x$ $=$ 0.08, and is almost invariable for $x$ $=$ 0.06. Complex pressure and Ru-doping effects on ${H}_{\mathrm{E}}$ and ${H}_{\mathrm{C}}$ are explained within a model involving size-variable nanoscale FM regions (droplets) embedded in an AFM matrix. The enhancement of EB with increasing pressure is attributed to the reduction in the FM droplet size, evidenced by both pressure dependence of spontaneous FM moment and ${H}_{\mathrm{E}}$ dependence upon cooling field ${H}_{\mathrm{cool}}$. The impact of FM droplet size on the EB was further evidenced by the magnetic field effect, which, in contrast to the pressure effect, leads to a growth of the FM droplets. The intricate ${H}_{\mathrm{C}}$ dependencies on both pressure and Ru content are understandable in a view of the transition from the multidomain state to the single-domain one, induced by droplet size decrease with increasing pressure or with doping lowering. Concisely, owing to the unique mechanism of valence modification, the external pressure appears to be an effective tool for controlling the EB and the coercivity in Ru-doped CaMnO${}_{3}$ perovskites.

The influence of pressure on the superconducting properties of GdBa1.5Sr0.5Cu3O6+x (x = 0.63−0.93) ceramics has been studied. The pressure effect on Tc strongly depends on the oxygen content. Unlike YBa2Cu3O6+x the d T c d P value increases monotonically with decreasing x without the peak for x ≈ 0.7. The value d T c d P = 13.7 K (for x = 0.63) is the highest value for HTSC's of the 123 type. Under a prolonged action of pressure at room temperature the relaxation of the critical parameters (Tc, Hc1) as well as hysteretic phenomena in the case of pressure decrease have been observed. These effects are interpreted as being due to oxygen ordering in the CuO chains. The effect resulting from the oxygen ordering under pressure depends stronger on the oxygen index x than the intrinsic pressure effect connected only with the compression of the unit cell.

The appearance of superconductivity and the relaxation of T c to the equilibrium value T c ≈30 K in a period of five days were observed in the tetragonal ceramic NdBa2Cu3O6.67 under a pressure of 1 GPa. The superconducting phase vanishes 1.3 h after the pressure is released. This behavior is explained by the charge redistribution occurring as a result of pressure-induced ordering of oxygen in the CuOx planes.

The influence of hydrostatic pressure up to 1 GPa on the transition temperature to the superconducting state in orthorhombic samples of GdBa1.5Sr0.5Cu3Ox with the oxygen content x=6.63, 6.73 and 6.93 has been studied. The observations of Tc changes were done by means of DC magnetic-susceptibility measurements. A monotonical strong increase of the pressure effect, dTc/dP, with decreasing x value has been found. This behavior differs from the complex character of the dependence of dTc/dP on the oxygen content in YBa2Cu3Ox. In the case of GdBa1.5Sr0.5Cu3O6.63 a pressure effect dTc/dP as high as 13.7 K/GPa was obtained, higher than that reported for YBa2Cu3O6.71 (11.5 K/GPa) in the region of the ortho(I)-to-ortho(II) transition.

Magnetic properties of self-doped LaMn1−xO3 manganites (0⩽x⩽0.06) under hydrostatic pressure up to 12 kbar have been investigated. Samples with x=0 and 0.02 are antiferromagnetic insulators with a Neel temperature TN=138 K and 124 K, respectively. Materials with x=0.04 and 0.06 are ferromagnetic with a Curie temperature TC close to 110 K. With increasing self-doping, the ferromagnetic moment at T=5 K increases significantly while the pressure coefficient of TN decreases significantly. Pressure dependences of TC and of spontaneous magnetization are markedly different. For x=0.04, both quantities increase under increasing pressure. However, for x=0.06 transition temperature becomes pressure independent while magnetization markedly decreases with increasing pressure. Suppression of the ferromagnetism under pressure is tentatively attributed to the development of antiferromagnetic domains capable of competing with the ferromagnetic order under pressure.

Exchange bias effect in CaMn1-xRexO3 (x ≤ 0.1) has been investigated. The effect is very small in the samples doped at x = 0.02 and 0.04, but increases monotonously with further increase in Re doping. For x = 0.1, both vertical and horizontal shifts in hysteresis loop of field cooled sample decrease monotonously with increasing temperature and vanish above 70 K, while coercivity disappears only above 90 K upon approaching the Néel temperature. Exchange bias field, coercivity, and remanence asymmetry depend sensitively on temperature and maximal measuring field. Magnetic training effect has been studied for x = 0.06, 0.08, 0.1 samples and analyzed using a spin relaxation model. The observed exchange bias is attributed to the low-temperature phase separation into ferromagnetic clusters and the G-type and/or C-type antiferromagnetic matrix.

The pressure effect up to 1 GPa on the magnetic T−H diagram of GdBa 2 Cu 3 O 6.3 single crystals is studied by means of AC susceptibility measurements in the temperature range 0.05–4 K. The spin flop (SF) transition observed below 1 K in magnetic fields applied along the C -axis has the same character as in a 2D antiferromagnet. The SF transition field, H sh (0) = 13 kOe, is pressure-independent but the SF phase region is extended under pressure, due to the increase of the exchange interaction and the decrease of the anisotropy field. The magnetic behavior under pressure is described in the model of a two-sublattice antiferromagnet with anisotropic intralayer exchange interaction and single ion anisotropy.

Magnetization, FMR and sound velocities were measured in La 0.8 Sr 0.2 MnO 3 single crystals in the vicinity of the structural phase transition ( T s ). A strong jump in sound velocities was observed near T s . The temperature dependences of sound velocities and magnetization show the hysteresis characteristic of a first-order phase transition. The magnetization behavior indicates that the structural phase transition is accompanied by a magnetic phase transition of the spin reorientation type. It was shown that properties of the investigated single crystals are influenced by the presence of a twin structure. The existence of the twin structure was confirmed by FMR measurements.