nkhani

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The maginito katundu SrFe12O19 (SFO) molimba hexaferrite amawongoleredwa ndi zovuta ubale microstructure ake, amene amatsimikizira kufunika kwawo kwa okhazikika maginito ntchito. Sankhani gulu la SFO nanoparticles akamagwira Sol-gel osakaniza mowiriza kuyaka kaphatikizidwe, ndi kuchita mozama structural X-ray ufa diffraction (XRPD) makhalidwe ndi G (L) mzere mbiri kusanthula. Kugawidwa kwa kukula kwa crystallite kumasonyeza kudalira koonekeratu kwa kukula kwake motsatira njira ya [001] pa njira yophatikizira, zomwe zimapangitsa kuti pakhale mapangidwe a crystallites. Kuonjezera apo, kukula kwa SFO nanoparticles kunatsimikiziridwa ndi kusanthula kwa ma electron microscopy (TEM), ndipo chiwerengero cha ma crystallites mu particles chinayesedwa. Zotsatirazi zawunikidwa kuti ziwonetsere mapangidwe a mayiko amodzi omwe amalamulira pansi pa mtengo wovuta kwambiri, ndipo mphamvu yotsegulira imachokera ku miyeso ya magnetization yomwe imadalira nthawi, yomwe imayang'ana kuwunikira njira yosinthira magnetization ya zipangizo zolimba zamaginito.
Zida za maginito za nano-scale zimakhala ndi tanthauzo lalikulu la sayansi ndi luso lamakono, chifukwa maginito awo amawonetsa makhalidwe osiyana kwambiri poyerekeza ndi kukula kwake, zomwe zimabweretsa malingaliro atsopano ndi ntchito1,2,3,4. Pakati zipangizo nanostructured, M-mtundu hexaferrite SrFe12O19 (SFO) wakhala phungu wokongola kwa okhazikika maginito ntchito5. M'malo mwake, m'zaka zaposachedwa, ntchito zambiri zofufuza zachitika pakukonza zida zozikidwa pa SFO pa nanoscale kudzera m'njira zosiyanasiyana zophatikizira ndi kukonza kuti ziwongolere kukula, mawonekedwe, ndi maginito6,7,8. Kuphatikiza apo, idalandira chidwi chachikulu pakufufuza ndi kukonza njira zolumikizirana zosinthana9,10. Maginito ake apamwamba a magnetocrystalline anisotropy (K = 0.35 MJ / m3) yolunjika pamodzi ndi c-axis ya hexagonal lattice 11,12 ndi zotsatira zachindunji cha mgwirizano wovuta pakati pa maginito ndi mawonekedwe a crystal, crystallites ndi kukula kwa mbewu, morphology ndi kapangidwe. Choncho, kulamulira makhalidwe omwe ali pamwambawa ndi maziko okwaniritsa zofunikira zenizeni. Chithunzi 1 chikuwonetsa gulu la danga la hexagonal P63/mmc la SFO13, ndi ndege yofananira ndi chithunzithunzi cha kafukufuku wa mbiri ya mzere.
Zina mwazokhudzana ndi kuchepetsa kukula kwa tinthu tating'onoting'ono ta ferromagnetic, kupangidwa kwa dera limodzi laling'ono pansi pamtengo wovuta kumabweretsa kuwonjezeka kwa maginito anisotropy (chifukwa chapamwamba pamtunda mpaka chiwerengero cha voliyumu), chomwe chimatsogolera kumunda wokakamiza14,15. Dera lalikulu lomwe lili pansi pa gawo lofunika kwambiri (DC) muzinthu zolimba (mtengo wamba ndi pafupifupi 1 µm), ndipo umatanthauzidwa ndi zomwe zimatchedwa kukula kogwirizana (DCOH) 16: izi zikutanthauza njira yaying'ono kwambiri ya demagnetization mu kukula kogwirizana. (DCOH) , Kuwonetsedwa ngati mphamvu yowonjezera (VACT) 14. Komabe, monga momwe tawonetsera pa Chithunzi 2, ngakhale kuti kukula kwa kristalo kuli kochepa kuposa DC, njira yosinthira ikhoza kukhala yosagwirizana. Mu nanoparticle (NP) zigawo zikuluzikulu, voliyumu yovuta ya kusintha kumadalira kukhuthala kwa maginito (S), ndipo kudalira kwake kwa maginito kumapereka chidziwitso chofunikira chokhudza kusintha kwa NP magnetization17,18.
Pamwamba: Chiwonetsero cha chisinthiko cha gawo lokakamiza ndi kukula kwa tinthu, kuwonetsa njira yosinthira maginito (yosinthidwa kuchokera ku 15). SPS, SD, ndi MD imayimira superparamagnetic state, single domain, and multidomain, motsatana; DCOH ndi DC amagwiritsidwa ntchito polumikizana m'mimba mwake ndi m'mimba mwake yovuta, motsatana. Pansi: Zojambula za tinthu tating'onoting'ono tosiyanasiyana, towonetsa kukula kwa makristalo kuchokera ku kristalo imodzi kupita ku polycrystalline. ndi kusonyeza crystallite ndi tinthu kukula, motero.
Komabe, pa nanoscale, zinthu zatsopano zovuta zayambitsidwanso, monga kuyanjana kwamphamvu kwa maginito pakati pa tinthu tating'onoting'ono, kugawa kukula, mawonekedwe a tinthu, kusokonezeka kwapamwamba, ndi njira yophweka ya magnetization, zonse zomwe zimapangitsa kusanthula kukhala kovuta19, 20 . Zinthu izi zimakhudza kwambiri kugawa chotchinga mphamvu ndipo zimayenera kuganiziridwa mosamalitsa, potero zimakhudza njira yosinthira maginito. Pamaziko awa, ndikofunikira kwambiri kumvetsetsa bwino kulumikizana pakati pa voliyumu yamaginito ndi mawonekedwe amtundu wa M-mtundu wa hexaferrite SrFe12O19. Choncho, monga dongosolo lachitsanzo, tinagwiritsa ntchito ma SFO okonzedwa ndi njira yapansi-mmwamba sol-gel, ndipo posachedwapa tachita kafukufuku. Zotsatira zam'mbuyo zimasonyeza kuti kukula kwa crystallites kuli mumtundu wa nanometer, ndipo izo, pamodzi ndi mawonekedwe a crystallites, zimadalira chithandizo cha kutentha chomwe chimagwiritsidwa ntchito. Kuonjezera apo, crystallinity ya zitsanzo zoterezi zimadalira njira yophatikizira, ndipo kusanthula mwatsatanetsatane kumafunika kumveketsa mgwirizano pakati pa crystallites ndi kukula kwa tinthu. Pofuna kuwulula ubalewu, kusanthula kwa ma electron microscopy (TEM) kophatikizana ndi njira ya Rietveld ndi kusanthula mbiri ya mzere wa kuchuluka kwa X-ray powder diffraction, magawo a crystal microstructure (ie, crystallites ndi kukula kwa tinthu, mawonekedwe) adawunikidwa mosamala. . XRPD) mode. Makhalidwe apangidwe amafuna kudziwa mawonekedwe a anisotropic a nanocrystallites omwe adapezedwa ndikutsimikizira kuthekera kwa kusanthula mbiri ya mzere ngati njira yamphamvu yozindikiritsa kufalikira kwapamwamba kwambiri pamitundu ya nanoscale ya (ferrite). Iwo anapeza kuti voliyumu-wolemera crystallite kukula kugawa G (L) kwambiri zimadalira crystallographic malangizo. Mu ntchito iyi, tikuwonetsa kuti njira zowonjezera ndizofunikadi kuti muchotse molondola magawo okhudzana ndi kukula kuti afotokoze bwino mawonekedwe ndi maginito a zitsanzo za ufa. Njira ya reverse magnetization idaphunziridwanso kuti imveketse ubale pakati pa mawonekedwe a morphological ndi machitidwe a maginito.
Kusanthula kwa Rietveld kwa X-ray powder diffraction (XRPD) deta imasonyeza kuti kukula kwa crystallite pamodzi ndi c-axis kungasinthidwe ndi chithandizo choyenera cha kutentha. Zikuwonetsa mwatsatanetsatane kuti kufalikira kwapamwamba komwe kumawonedwa pachitsanzo chathu kungakhale chifukwa cha mawonekedwe a anisotropic crystallite. Kuphatikiza apo, kusasinthika pakati pa mainchesi omwe amawunikidwa ndi Rietveld ndi chithunzi cha Williamson-Hall ( ndi mu Table S1) ikuwonetsa kuti ma crystallites ndi pafupifupi opanda zovuta ndipo palibe kupunduka kwamapangidwe. Chisinthiko cha kukula kwa crystallite kagawidwe kosiyanasiyana kumayang'ana chidwi chathu pa kukula kwa tinthu tating'ono. Kusanthula si kophweka, chifukwa chitsanzo akamagwira Sol-gel osakaniza mowiriza kuyaka wapangidwa agglomerates wa particles ndi porous structure6,9 , makumi awiri ndi chimodzi. TEM imagwiritsidwa ntchito pophunzira momwe zamkati mwachitsanzo choyesera mwatsatanetsatane. Zithunzi zowoneka bwino zowoneka bwino zikufotokozedwa mu Chithunzi 3a-c (kuti mumve zambiri za kusanthula, chonde onani gawo 2 lazowonjezera). Chitsanzocho chimakhala ndi tinthu tating'onoting'ono tokhala ndi mawonekedwe a tiziduswa tating'ono. Mapulateleti amalumikizana pamodzi kupanga ma porous aggregates a kukula ndi mawonekedwe osiyanasiyana. Kuti muyerekeze kukula kwa mapulateleti, gawo la tinthu 100 lachitsanzo chilichonse lidayesedwa pamanja pogwiritsa ntchito pulogalamu ya ImageJ. Kuzungulira kwa bwalo lofanana ndi gawo lomwelo la tinthu tating'ono monga mtengo wake umachokera ku kukula kwake kwa chidutswa chilichonse choyezedwa. Zotsatira za zitsanzo za SFOA, SFOB ndi SFOC ndizofupikitsidwa mu Chithunzi 3d-f, ndipo mtengo wapakati wapakati umanenedwanso. Kuonjezera kutentha kwa processing kumawonjezera kukula kwa tinthu tating'onoting'ono ndi kugawa m'lifupi mwake. Kuchokera poyerekeza pakati pa VTEM ndi VXRD (Table 1), zikhoza kuwoneka kuti pa zitsanzo za SFOA ndi SFOB, chiwerengero cha crystallites pa tinthu chimasonyeza chikhalidwe cha polycrystalline cha lamellae. Mosiyana ndi zimenezi, kuchuluka kwa tinthu ta SFOC ndikufanana ndi voliyumu ya crystallite, kusonyeza kuti ambiri mwa lamellae ndi makhiristo amodzi. Tikuwonetsa kuti kukula kowonekera kwa TEM ndi X-ray diffraction ndi yosiyana, chifukwa pamapeto pake, tikuyesa cholumikizira chobalalika (chikhoza kukhala chaching'ono kuposa flake wamba): Kuphatikiza apo, zolakwika zazing'ono zomwe zimabalalika izi. madera adzawerengedwa ndi diffraction .
Zithunzi zowala za TEM za (a) SFOA, (b) SFOB ndi (c) SFOC zimasonyeza kuti zimapangidwa ndi tinthu tating'onoting'ono tokhala ngati mbale. Kugawidwa kofananirako kumawonetsedwa mu histogram ya gulu (df).
Monga tawoneranso pakuwunika koyambirira, ma crystallites mu zitsanzo za ufa weniweni amapanga polydisperse system. Popeza njira ya X-ray imakhudzidwa kwambiri ndi chipika chobalalika chogwirizana, kufufuza mozama za deta ya ufa wa diffraction kumafunika kufotokozera ma nanostructures abwino. Apa, kukula kwa ma crystallites akukambidwa kudzera mu mawonekedwe a voliyumu yolemerera kukula kwa crystallite kukula kwa G (L) 23, yomwe ingatanthauzidwe kuti ndi mwayi wopeza ma crystallites a mawonekedwe ndi kukula kwake, ndipo kulemera kwake kuli kolingana ndi izo. Voliyumu, mu chitsanzo chofufuzidwa. Ndi mawonekedwe a prismatic crystallite, kukula kwa kristalo wolemera voliyumu (utali wam'mbali mwa [100], [110] ndi [001] mayendedwe) ukhoza kuwerengedwa. Choncho, tinasankha zitsanzo zonse zitatu za SFO ndi kukula kwake kwa tinthu tating'onoting'ono ta anisotropic flakes (onani Buku la 6) kuti tiwone momwe njirayi ikuyendera kuti tipeze kugawa kwabwino kwa crystallite kwa nano-scale. Pofuna kuyesa mawonekedwe a anisotropic a ma crystallites a ferrite, kusanthula kwa mzere kunachitika pa data ya XRPD ya nsonga zosankhidwa. Zitsanzo za SFO zoyesedwa zinalibe zosokoneza (zoyera) zapamwamba kuchokera kumagulu omwewo a ndege za kristalo, kotero kunali kosatheka kulekanitsa chopereka chokulitsa mzere kuchokera ku kukula ndi kupotoza. Panthawi imodzimodziyo, kuwonjezereka kowoneka kwa mizere yowonongeka kumakhala kosavuta chifukwa cha kukula kwake, ndipo mawonekedwe amtundu wa crystallite amatsimikiziridwa kupyolera mu kufufuza kwa mizere ingapo. Chithunzi 4 chikufanizira ntchito yogawa kukula kwa kristalo wolemera voliyumu G (L) motsatira njira yodziwika bwino ya crystallographic. Mtundu wamba wa kugawa kukula kwa crystallite ndikugawa kwa lognormal. Chikhalidwe chimodzi mwa magawo onse omwe amapezeka ndi kukula kwawo kosagwirizana. Nthawi zambiri, kugawa uku kungabwere chifukwa cha njira yomwe imatanthauzidwa ngati tinthu tating'onoting'ono. Kusiyana pakati pa kukula kwachiwerengero chowerengeka cha nsonga yosankhidwa ndi mtengo wochotsedwa ku kukonzanso kwa Rietveld kuli mkati mwamtundu wovomerezeka (poganizira kuti njira zowonetsera zida ndizosiyana pakati pa njirazi) ndipo ndizofanana ndi zomwe zimachokera ku gulu logwirizana la ndege ndi Debye Kukula kwapakati komwe kumapezeka kumagwirizana ndi Scherrer equation, monga momwe tawonetsera mu Table 2. Mchitidwe wa voliyumu wa crystallite kukula kwa njira ziwiri zosiyana zowonetsera ndizofanana kwambiri, ndipo kupatuka kwa kukula kwakukulu kumakhala kochepa kwambiri. Ngakhale pakhoza kukhala kusagwirizana ndi Rietveld, mwachitsanzo, pankhani ya (110) kuwonetsera kwa SFOB, kungakhale kogwirizana ndi kutsimikiza kolondola kwa maziko kumbali zonse ziwiri za chiwonetsero chosankhidwa pa mtunda wa 1 digiri 2θ pamtundu uliwonse. malangizo. Komabe, mgwirizano wabwino kwambiri pakati pa matekinoloje awiriwa umatsimikizira kufunika kwa njirayi. Kuchokera pakuwunika kufalikira kwapamwamba, zikuwonekeratu kuti kukula kwake komweko [001] kumadalira mwachindunji njira yophatikizira, zomwe zimapangitsa kuti pakhale ma crystallites a flaky mu SFO6,21 opangidwa ndi sol-gel. Mbaliyi imatsegula njira yogwiritsira ntchito njirayi popanga ma nanocrystals okhala ndi mawonekedwe okonda. Monga tonse tikudziwa, mawonekedwe a kristalo ovuta a SFO (monga momwe tawonetsera pa Chithunzi 1) ndiye maziko a khalidwe la ferromagnetic la SFO12, kotero mawonekedwe ndi kukula kwake kungasinthidwe kuti akwaniritse mapangidwe a chitsanzo cha ntchito (monga nthawi zonse. zokhudzana ndi maginito). Tikuwonetsa kuti kusanthula kukula kwa crystallite ndi njira yamphamvu yofotokozera anisotropy ya mawonekedwe a crystallite, ndikulimbitsanso zotsatira zomwe zidapezedwa kale.
(a) SFOA, (b) SFOB, (c) SFOC yosankhidwa yowonetsera (100), (110), (004) voliyumu yolemerera kukula kwa crystallite kugawa G(L).
Kuti tiwone momwe ndondomekoyi ikuyendera kuti tipeze kukula kwa crystallite kukula kwa zipangizo za nano-ufa ndikuziyika ku zovuta zowonongeka, monga momwe tawonetsera pa Chithunzi 5, tatsimikizira kuti njirayi ndi yothandiza mu zipangizo za nanocomposite (zodziwika bwino). Kulondola kwa mlanduwu kumapangidwa ndi SrFe12O19/CoFe2O4 40/60 w/w %). Zotsatira izi zimagwirizana kwathunthu ndi kusanthula kwa Rietveld (onani mawu ofotokozera a Chithunzi 5 poyerekeza), ndipo poyerekeza ndi dongosolo la gawo limodzi, SFO nanocrystals ikhoza kuwonetsa morphology yofanana ndi mbale. Zotsatirazi zikuyembekezeredwa kuti zigwiritse ntchito kusanthula kwa mbiri ya mzerewu ku machitidwe ovuta kwambiri momwe magawo angapo a kristalo amatha kuphatikizira popanda kutaya chidziwitso chokhudza mapangidwe awo.
Kugawa kwamtundu wa crystallite wolemera kwambiri G (L) wazithunzi zosankhidwa za SFO ((100), (004)) ndi CFO (111) mu nanocomposites; poyerekeza, zofananira zowunikira za Rietveld ndi 70 (7), 45 (6) ndi 67 (5) nm6.
Monga momwe tawonetsera pa Chithunzi 2, kutsimikiza kwa kukula kwa mphamvu ya maginito ndi kulingalira koyenera kwa voliyumu ya thupi ndilo maziko a kufotokozera machitidwe ovutawa komanso kumvetsetsa bwino kuyanjana ndi dongosolo la mapangidwe pakati pa maginito particles. Posachedwapa, machitidwe a maginito a zitsanzo za SFO adaphunziridwa mwatsatanetsatane, ndi chidwi chapadera pa kusintha kwa magnetization, kuti aphunzire gawo losasinthika la magnetic susceptibility (χirr) (Chithunzi S3 ndi chitsanzo cha SFOC)6. Kuti timvetsetse mozama za njira yosinthira maginito mu nanosystem iyi, tidachita kuyeza kwa maginito opumula m'malo obwerera (HREV) titadzaza njira yoperekedwa. Ganizirani \(M\left(t\right)\proptoSln\left(t\right)\) (onani Chithunzi 6 ndi zowonjezera kuti mumve zambiri) ndiyeno pezani voliyumu yotsegulira (VACT). Popeza imatha kufotokozedwa ngati gawo laling'ono kwambiri lazinthu zomwe zingasinthidwe mokhazikika pamwambo, chizindikirochi chikuyimira voliyumu ya "magnetic" yomwe ikukhudzidwa ndikusintha. Mtengo wathu wa VACT (onani Table S3) umagwirizana ndi gawo lomwe lili ndi mainchesi pafupifupi 30 nm, lomwe limatanthauzidwa ngati mainchesi ogwirizana (DCOH), omwe amafotokoza malire apamwamba akusintha kwa maginito kwadongosolo mozungulira mozungulira. Ngakhale pali kusiyana kwakukulu mu thupi la tinthu ting'onoting'ono (SFOA ndi 10 nthawi zazikulu kuposa SFOC), mfundozi ndizokhazikika komanso zazing'ono, zomwe zimasonyeza kuti njira yosinthira maginito ya machitidwe onse imakhala yofanana (yogwirizana ndi zomwe timadzinenera ndi single domain system) 24 . Pamapeto pake, VACT ili ndi voliyumu yaying'ono kwambiri kuposa XRPD ndi TEM kusanthula (VXRD ndi VTEM mu Table S3). Choncho, tikhoza kunena kuti kusinthana sikungochitika kokha kupyolera mu kasinthasintha wogwirizana. Dziwani kuti zotsatira zopezedwa pogwiritsa ntchito maginitometer osiyanasiyana (Chithunzi S4) zimapereka milingo yofananira ya DCOH. Pachifukwa ichi, ndikofunika kwambiri kufotokozera zovuta ziwiri za gawo limodzi laling'ono (DC) kuti mudziwe njira yabwino yosinthira. Malinga ndi kusanthula kwathu (onani zowonjezera), titha kunena kuti VACT yomwe idapezedwa imakhudza njira yosinthira, chifukwa DC (~ 0.8 µm) ili kutali kwambiri ndi DC (~ 0.8 µm) ya tinthu tating'onoting'ono, ndiye kuti, mapangidwe ankalamulira makoma si Ndiye analandira thandizo amphamvu ndi kupeza limodzi ankalamulira kasinthidwe. Chotsatirachi chikhoza kufotokozedwa ndi mapangidwe a mgwirizano wa domain25, 26. Timaganiza kuti crystallite imodzi imatenga nawo mbali pamtundu wolumikizana, womwe umafikira ku tinthu tating'onoting'ono tating'onoting'ono tating'onoting'ono tazinthu izi27,28. Ngakhale njira za X-ray zimangoganizira za microstructure yabwino ya madera (microcrystals), miyeso yopumula maginito imapereka umboni wa zochitika zovuta zomwe zingachitike mu SFOs za nanostructured. Choncho, mwa kukhathamiritsa kukula kwa nanometer kwa mbewu za SFO, ndizotheka kupewa kusinthira kuzinthu zambiri zowonongeka, potero kusunga kukakamiza kwakukulu kwa zipangizozi.
(a) The nthawi amadalira maginito pamapindikira a SFOC anayeza pa osiyana n'komwe munda HREV mfundo pambuyo machulukitsidwe pa-5 T ndi 300 K (akusonyeza pafupi deta experimental) (maginito ndi normalized malinga ndi kulemera kwa chitsanzo); kuti zimveke bwino, Chigawochi chimasonyeza deta yoyesera ya 0,65 T munda (bwalo lakuda), lomwe liri ndi zoyenera kwambiri (mzere wofiira) (magnetization imasinthidwa kukhala mtengo woyambirira M0 = M (t0)); (b) maginito viscosity (S) yofanana ndi SFOC A ntchito ya munda (mzere ndi chitsogozo cha diso); (c) kachipangizo kamene kamakhala ndi tsatanetsatane wa kutalika kwa thupi/maginito.
Nthawi zambiri, kusintha kwa maginito kumatha kuchitika kudzera munjira zingapo zakumaloko, monga kuphatikizika kwa khoma, kufalitsa, kusindikiza ndi kutulutsa. Pankhani ya single-domain ferrite particles, njira yotsegulira ndi nucleation-mediated ndipo imayambitsidwa ndi kusintha kwa maginito kocheperako kuposa voliyumu yonse yosinthira maginito (monga momwe tawonetsera pa Chithunzi 6c)29.
The kusiyana pakati pa magnetism yovuta ndi awiri thupi zikutanthauza kuti mode incoherent ndi concomitant chochitika cha kusintha maginito ankalamulira, amene mwina chifukwa cha inhomogeneities zinthu ndi pamwamba kusamvana, amene amakhala correlated pamene tinthu kukula ukuwonjezeka 25, chifukwa cha kupatuka kwa zinthu. yunifolomu magnetization state.
Choncho, tikhoza kunena kuti m'dongosolo lino, njira yosinthira maginito ndizovuta kwambiri, ndipo kuyesetsa kuchepetsa kukula kwa nanometer sikelo kumagwira ntchito yofunika kwambiri pakugwirizana pakati pa microstructure ya ferrite ndi magnetism. .
Kumvetsetsa ubale wovuta pakati pa kapangidwe, mawonekedwe ndi maginito ndiye maziko opangira ndikupanga mapulogalamu amtsogolo. Kusanthula kwa mzere wamtundu wosankhidwa wa XRPD wa SrFe12O19 kunatsimikizira mawonekedwe a anisotropic a nanocrystals omwe amapezedwa ndi njira yathu yophatikizira. Kuphatikizidwa ndi kusanthula kwa TEM, chikhalidwe cha polycrystalline cha tinthu ichi chinatsimikiziridwa, ndipo pambuyo pake chinatsimikiziridwa kuti kukula kwa SFO komwe kunkafufuzidwa mu ntchitoyi kunali kochepa kusiyana ndi gawo limodzi lofunika kwambiri, ngakhale umboni wa kukula kwa crystallite. Pamaziko awa, tikupangira njira yosasinthika ya magnetization potengera kukhazikitsidwa kwa dera lolumikizana lomwe limapangidwa ndi ma crystallites olumikizidwa. Zotsatira zathu zimatsimikizira kulumikizana kwapafupi pakati pa particle morphology, kapangidwe ka kristalo ndi kukula kwa crystallite komwe kuli pamlingo wa nanometer. Kafukufukuyu akufuna kumveketsa bwino njira yosinthira maginito yazinthu zolimba za nanostructured maginito ndikuzindikira momwe mawonekedwe a microstructure amagwirira ntchito.
Zitsanzozo zinapangidwa pogwiritsa ntchito citric acid monga chelating agent / mafuta molingana ndi njira yoyaka moto ya sol-gel, yomwe inafotokozedwa mu Reference 6. Mikhalidwe yophatikizirayo inakonzedwa kuti ipeze mitundu itatu yosiyana ya zitsanzo (SFOA, SFOB, SFOC), zomwe zinali zopezedwa ndi mankhwala oyenera a annealing pa kutentha kosiyana (1000, 900, ndi 800 ° C, motsatana). Table S1 ikufotokoza mwachidule za maginito ndikupeza kuti ndizofanana. Nanocomposite SrFe12O19/CoFe2O4 40/60 w/w% inakonzedwanso chimodzimodzi.
Mawonekedwe a diffraction adayesedwa pogwiritsa ntchito ma radiation a CuKα (λ = 1.5418 Å) pa Bruker D8 powder diffractometer, ndipo m'lifupi mwake chowunikira chinayikidwa ku 0.2 mm. Gwiritsani ntchito kauntala ya VANTEC kuti mutenge deta mu 2θ osiyanasiyana 10-140 °. Kutentha panthawi yojambula deta kunasungidwa pa 23 ± 1 °C. Kuwonetserako kumayesedwa ndi teknoloji ya sitepe-ndi-scan, ndipo kutalika kwa mayesero onse ndi 0.013 ° (2theta); nsonga yapamwamba kwambiri ya mtunda woyezera ndi-2.5 ndi + 2.5 ° (2theta). Pachimake chilichonse, kuchuluka kwa 106 quanta kumawerengedwa, pomwe kumchira kuli pafupifupi 3000 quanta. Zisonga zingapo zoyeserera (zolekanitsidwa kapena kupitirana pang'ono) zidasankhidwa kuti ziwunikidwe nthawi imodzi: (100), (110) ndi (004), zomwe zidachitika pamakona a Bragg pafupi ndi ngodya ya Bragg ya mzere wolembetsa wa SFO. Kuzama kwakuyesera kunakonzedwa chifukwa cha Lorentz polarization factor, ndipo maziko adachotsedwa ndikusintha kwa mzere. NIST yokhazikika ya LaB6 (NIST 660b) idagwiritsidwa ntchito kuwongolera chida ndi kufalikira kwa mawonekedwe. Gwiritsani ntchito njira ya LWL (Louer-Weigel-Louboutin) deconvolution 30,31 kuti mupeze mizere yosiyana kwambiri. Njirayi ikugwiritsidwa ntchito mu pulogalamu yowunikira mbiri PROFIT-software32. Kuchokera pakugwirizana kwa kuchuluka kwamphamvu kwachitsanzo ndi muyezo wokhala ndi pseudo Voigt ntchito, mizere yolondola yofananira f(x) imachotsedwa. Ntchito yogawa kukula kwa G(L) imatsimikiziridwa kuchokera ku f(x) potsatira ndondomeko yomwe ili mu Buku la 23. Kuti mudziwe zambiri, chonde onani zowonjezera. Monga chowonjezera pakuwunika kwa mzere, pulogalamu ya FULLPROF imagwiritsidwa ntchito popanga Rietveld kusanthula pa data ya XRPD (zambiri zitha kupezeka ku Maltoni et al. 6). Mwachidule, mu chitsanzo cha Rietveld, nsonga zowonongeka zimafotokozedwa ndi ntchito yosinthidwa ya Thompson-Cox-Hastings pseudo Voigt. Kusintha kwa LeBail kwa data kunachitika pa muyezo wa NIST LaB6 660b kuwonetsa momwe chidacho chathandizira pakukulitsa kwambiri. Malinga ndi FWHM yowerengeka (m'lifupi mwathunthu pa theka la kuchuluka kwamphamvu), equation ya Debye-Scherrer ingagwiritsidwe ntchito kuwerengera kukula kwapakati pagawo lophatikizana lomwaza makristalo:
Pomwe λ ndi mawonekedwe a X-ray radiation, K ndiye mawonekedwe (0.8-1.2, nthawi zambiri amakhala 0.9), ndipo θ ndi ngodya ya Bragg. Izi zikugwira ntchito ku: chiwonetsero chosankhidwa, ndege yofananira ndi mawonekedwe onse (10-90 °).
Kuphatikiza apo, microscope ya Philips CM200 yomwe ikugwira ntchito pa 200 kV komanso yokhala ndi ulusi wa LaB6 idagwiritsidwa ntchito posanthula TEM kuti adziwe zambiri za particle morphology ndi kugawa kukula.
Muyezo wopumula wa maginito umachitidwa ndi zida ziwiri zosiyana: Physical Property Measurement System (PPMS) kuchokera ku Quantum Design-Vibrating Sample Magnetometer (VSM), yokhala ndi 9 T superconducting maginito, ndi MicroSense Model 10 VSM yokhala ndi electromagnet. Munda ndi 2 T, chitsanzocho chimadzaza m'munda (μ0HMAX: -5 T ndi 2 T, motsatira chida chilichonse), ndiyeno gawo lakumbuyo (HREV) limagwiritsidwa ntchito kuti libweretse chitsanzo kumalo osinthira (pafupi ndi HC). ), ndiyeno kuwonongeka kwa magnetization kumalembedwa ngati ntchito ya nthawi yopitilira mphindi 60. Kuyeza kumachitidwa pa 300 K. Voliyumu yolumikizira yofananira imawunikidwa kutengera milingo yomwe yafotokozedwa muzowonjezera.
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