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1

Magnetotransport and magnetic properties of manganites doped with iron and aluminum

Troyanchuk I., Bushinsky M., Tereshko N., Fedotova V.

Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej

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2017

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Nr 11

5--10

EN

The single crystals of La0.7Ba0.3(Mn1-xFex)O3 (x ≤ 0.28) and La0.7Ba0.3(Mn1-xAlx)O3 (x ≤ 0.15) compositions were grown using flux method and characterized by X-ray, electrical and magnetization measurements. The replacement of Mn ions by Al ions in the La0.7Ba0.3Mn1-xAlxO3 system leads to a decrease in the temperature to 311 K for the sample x=0.1. The Fe-doping above x=0.2 destroys a long range ferromagnetic order thus leading to a spin glass state. It is found that insulating spin glasses exhibit a large magnetoresistance in the paramagnetic region that is comparable to that for ferromagnetic crystals showing metal–insulator transition near TC.

PL

Monokryształy La0,7Ba0,3(Mn1-xFex)O3 (x ≤ 0,28) i La 0,7Ba 0,3 (Mn1-xAlx)O3 (x ≤ 0,15) wyhodowano metodą strumieniową i charakteryzowano poprzez badania rentgenowskie, pomiary elektryczne i magnetyzacyjne. Zastąpienie jonów Mn jonami Al w układzie La0,7Ba0,3Mn1-xAlxO3 prowadzi do obniżenia temperatury do 311 K dla próbki x = 0,1. Domieszka Fe powyżej x = 0,2 niszczy ferromagnetyczny porządek dalekiego zasięgu atomów Fe, prowadząc w ten sposób do spinowego stanu typu szkła. Stwierdzono, że izolacyjny spinowy stan typu szkła wykazuje dużą rezystancję magnetyczną w obszarze paramagnetycznym, która jest porównywalna z kryształami ferromagnetycznymi i wykazują przejście metal-izolator w pobliżu TC.

2

Magnetic and magnetotransport properties of La0.5Sr0.5Co0.8Me0.2O3 (Me=Cr, Fe) cobaltites

Troyanchuk I., Bushinsky M., Tereshko N., Fedotova V.

Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej

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2015

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Nr 8

69--76

EN

Magnetic and magnetotransport properties of La0.5Sr0.5Co0.8Me0.2O3 (Me = Cr, Fe) stoichiometric cobaltites has been investigated in magnetic fields up to 14 T. It is shown that doping with Fe ions changes spontaneous magnetization only slightly herewith the Curie point significantly decreases. The chromium doping leads to dramatic decrease of magnetization and the Curie point and a strong increase in magnetoresistance at low temperature. The obtained results indicate that the magnetic interactions between Co and Fe are positive whereas those between Co and Cr ions are negative. Enhancement of magnetoresistance is attributed to the magnetic field induced transition from antiferromagnetic order to ferromagnetic one.

PL

Właściwości magnetyczne i magnetotransportowe stoichiometrycznych kobaltytów zbadano w polach magnetycznych do 14T. Ustalono, że domieszkowanie przez jony Fe zmienia namagnesowanie spontaniczne bardzo słabo w tym czasie jak punkt Curie obniża się znacząco. Domieszkowanie przez atomy chromu powoduje dramatyczne zmniejszenie namagnesowania i obniżenie punktu Curie i mocny wzrost magneto rezystancji w niskich temperaturach. Otrzymane rezultaty wskazują oddziaływanie magnetyczne pomiędzy Co i Fe jest pozytywne w tym czasie jak pomiędzy Co a Cr jest negatywne. Wzmocnienie magnetorezystancji przypisano do pola magnetycznego indukowanego przejściem z antyferromagnetycznego układu do ferromagnetycznego.

3

Introduction to n-body simulation of magnetorheological elastomer (MRE) microstructure forming process

Miedzińska D., Łazowski J., Boczkowska A.

Journal of KONES

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2010

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Vol. 17, No. 1

249-253

EN

Magnetorheological elastomers (MREs) are the materials with rheological properties which can be changed in a continuous way, rapidly and reversibly by the applied magnetic field. They are the solid analogues of magnetorheological fluids (MRFs), consisting of magnetically permeable particles (such as iron) added to a viscoelastic polymeric material prior to crosslinking. In the paper the introduction to the n-body simulation of the MRE microstructure forming process is presented. First, the basics of the n-body problem are presented as the planar three-body problem. It is well known, that the planar three-body problem is the problem describing the motion of three point masses in the plane under their mutual Newtonian gravitation. In the paper it is shown how that problem will be applied to the simulation of the phenomena that appeared when the external magnetic field is applied to the chaotically mixed iron particles in the liquid elastomer. Also the physical model of the interactions occurred in such structures are described. The assumptions shown in the paper will be then used for the development of the computer program which calculates the interactions between iron dipoles and describes the movement of the particles in the liquid elastomer under the magnetic field.

4

Oddziaływania elektronowe w dwucentrowych kompleksach nitrozylowych molibdenu

Włodarczyk A., Romańczyk P.

Wiadomości Chemiczne

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2008

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[Z] 62, 3-4

187-208

EN

Design and synthesis of redox active binuclear complexes in which metal centres are linked via bridging ligands enabling electronic and magnetic interactions between them are crucial for an understanding of key processes in chemistry and biology. In biological systems, such as proteins, electron transfer involves a charge transport over a considerable distance (>10 A*) [8-11,13-19]. On the other hand, long range electronic interactions are central in the development of potential elements for molecular electronics like molecule-sized wires, diodes, light activated switches, transistors (Fig. 1), logic gates etc. [1-7]. This article reviews some of the work performed in the area of bimetallic nitrosyl molybdenum complexes containing tris(3,5-dimethylpyrazol-1-yl)hydroborato ligand (Fig. 4). Numerous examples of mixed-valence species have been described, showing a wide range of behaviour from fully delocalized to valence-trapped systems of which electrochemical (voltammetry, Fig. 3), spectroscopic (EPR (Fig. 5), IR and UV-Vis/NIR spectroscopy) and magnetic susceptibility were studied. These results are summarised in Table 1. Many such complexes show exceptionally strong electrochemical (?Ef) and magnetic exchange interactions (J) between metal centres depending on the features of the bridging ligand such as length, degree of conjugation, dihedral angles between aromatic rings, substitution pattern, and symmetry [28, 41]. For example, in [{Mo(NO)(TpMe2)Cl}2{4,4'-bipy}] (Fig. 9) ?Ef equals 765 mV, being an order of magnitude greater when compared to the {Ru(NH3)5}2+/3+ analogue, and J = -33 cm-1 [43, 68, 69]. Using 3,3'-dimethyl-4,4'-bipy as a bridge forces a twist between the two pyridyl rings and decreases both ?Ef and J down to 380 mV and 3.5 cm-1, respectively [42, 71]. The introduction of a saturated section into the bridge, which breaks the conjugation, e.g. in 1,2-bis(4-pyridyl)ethane ligand, considerably decreases ?Ef (105 mV) but does not exclude electronic and magnetic through-bridge interactions [43]. Recently a series of bimetallic complexes based on {Mo(NO)(TpMe2)}2+ centres comprising n-alkanediolate bridges (Fig. 12) have been prepared. These species exhibited intermediate metal-metal interactions (310 mV in ethane-1,2-diolate) [54, 55] which prompted investigation of electronic interactions through saturated alkyl chains by DFT [64].

5

Review of luminescence and magnetic properties of antiferromagnetic KMnCl3, RbMnCl3, TlMnCl3 and (CnH2n+1NH3)2MnCl4 (n = 1, 2)

Pawłowska M., Wojciechowski W.

Materials Science

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2002

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Vol. 20, No. 1

122-122

EN

Phenomena connected with the energy transfer in perovskite-type antiferromagnetic materials KMnCl3, RbMnCl3, TlMnCl3 and (CnH2n+1NH3)2MnCl4 (n = 1, 2) dotted with Sm3+ and Eu3+ ions, are considered and discussed in this paper. The energy transfer in the compounds studied is proved to depend upon the magnetic interactions in them.

6

Magnetic interlayer coupling in the superlattices with rough interfaces

Jaroszewicz R.

Prace Naukowe. Chemia / Wyższa Szkoła Pedagogiczna w Częstochowie

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2001

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Vol. 5

103--107