Optical study of laser-induced magnetic phase transitions
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Vysoké učení technické v Brně. Fakulta strojního inženýrství
Abstract
Na vykonanie ultrarýchleho ukladania údajov na základe magnetických materiálov sa skúma nový spôsob sub-pikosekundovej magnetizácie. Železo-ródium sa navrhuje ako vhodný materiál, ktorý je schopný vykonávať laserom indukovanú magentizáciu. Prípravy na tento experiment pozostávajú z rastu vzorky pomocou metódy fyzikálneho naparovania magnetrónovým naprašovaním a následnej charakterizácie vzorky. Boli pripravené tri vzorky, každá s iným konceptom teplotného ladenia. Ukážka I je vyladená zmenou kompozície ( $Fe_{1-x}Rh_x$ ). Uloženie vzorky II na zafírový substrát indukované ťahovým napätím v rovine. Dopovaním uhlíka železo-ródiového tenkého filmu vzorky III. Tenkovrstvové vzorky sú charakterizované použitím vibračnej magnetometrie vzorky a optickej mikroskopie. Vibračná magnetometria vzorky poskytla spôsob zaznamenávania hysteréznych kriviek riadených poľom a čo je dôležitejšie, aj tepelne. Merania poskytli presné hodnoty teplôt fázového prechodu pre antiferomagnetické-k-feromagnetické a feromagnetické antiferomagnetické vzorky I, II a III boli určené na 325,9 K a 306 K, 321 K a 291 K, respektíve 311,8 K a 288 K. Boli zaznamenané charakteristické hodnoty saturácie magnetizácie, koercitívneho poľa, pomer zvyškovej magnetizácie a teplotného rozdielu medzi teplotami fázového prechodu. Vlastný kód v kombinácii s mikroskopickými obrázkami ponúkal dômyselné informácie o raste domén špecifických pre povrchovú oblasť. Kombinácia výsledkov oboch metód umožnila hlbšie pochopenie ‘’ako’’ a ‚‘‘kedy‘‘ vyššie uvedený magnetoštrukturálny fázový prechod. Ultrarýchla laserom indukovaná magnetizácia využíva vlastný dizajn lasera. Pozorovanie ožiareného tenkého filmu železo-ródia pomocou optickej mikroskopie ukazuje stabilné feromagnetické domény na vzorke v laserovej dráhe. Dospeli sme teda k záveru, že sú pripravené tenké vrstvy železo-ródia charakterizované magnetometriou ako funkcia teploty a bola úspešne vykonaná ultrarýchla magnetizácia indukovaná laserom.
To perform ultrafast storage of data based on magnetic materials, a new way of sub-picosecond magnetization is researched. Iron-Rhodium is suggested as convenient material which is capable of performing laser induced magnetization. Preparations for this experiment consists of sample growth using physical vapor deposition method of magnetron sputtering and subsequent sample characterization. Three samples were prepared, each with different concept of temperature tuning. Sample I is tuned via composition alteration ( $Fe_{1-x}Rh_x$ ). Sample II deposition onto a sapphire substrate induced tensile in-plane stress. By carbon doping Iron-Rhodium thin film of sample III. The thin film samples are characterized by using vibrating sample magnetometry and optical microscopy. Vibrating sample magnetometry granted a way of recording field driven and more importantly thermally driven hysteresis curves. Measurements yielded precise values of phase transition temperatures for antiferromagnetic-to-ferromagnetic and ferromagnetic-to-antiferromagnetic were detetermined for samples I, II, and III to be 325.9 K and 306 K, 321 K and 291 K, and 311.8 K and 288 K, respectively. Characteristic values of magnetization saturation, coercive field, residual magnetization and temperature difference between phase transition temperatures were recorded. Custom code in combination with microscopy images offered an insightful information on surface region specific domain growth. Combining results of both methods granted a deeper understanding of ''how'' and ''when'' aforementioned magnetostructural phase transition takes affect. The ultrashort laser induced magnetization utilizes a custom laser set-up. The observation of irradiated Iron-Rhodium thin film using optical microscopy shows stable ferromagnetic domains in a laser path pattern. Thus concluding that Iron-Rhodium thin films are prepared, characterized by magnetometry as a function of temperature, and the ultrafast laser induced magnetization was successfully performed.
To perform ultrafast storage of data based on magnetic materials, a new way of sub-picosecond magnetization is researched. Iron-Rhodium is suggested as convenient material which is capable of performing laser induced magnetization. Preparations for this experiment consists of sample growth using physical vapor deposition method of magnetron sputtering and subsequent sample characterization. Three samples were prepared, each with different concept of temperature tuning. Sample I is tuned via composition alteration ( $Fe_{1-x}Rh_x$ ). Sample II deposition onto a sapphire substrate induced tensile in-plane stress. By carbon doping Iron-Rhodium thin film of sample III. The thin film samples are characterized by using vibrating sample magnetometry and optical microscopy. Vibrating sample magnetometry granted a way of recording field driven and more importantly thermally driven hysteresis curves. Measurements yielded precise values of phase transition temperatures for antiferromagnetic-to-ferromagnetic and ferromagnetic-to-antiferromagnetic were detetermined for samples I, II, and III to be 325.9 K and 306 K, 321 K and 291 K, and 311.8 K and 288 K, respectively. Characteristic values of magnetization saturation, coercive field, residual magnetization and temperature difference between phase transition temperatures were recorded. Custom code in combination with microscopy images offered an insightful information on surface region specific domain growth. Combining results of both methods granted a deeper understanding of ''how'' and ''when'' aforementioned magnetostructural phase transition takes affect. The ultrashort laser induced magnetization utilizes a custom laser set-up. The observation of irradiated Iron-Rhodium thin film using optical microscopy shows stable ferromagnetic domains in a laser path pattern. Thus concluding that Iron-Rhodium thin films are prepared, characterized by magnetometry as a function of temperature, and the ultrafast laser induced magnetization was successfully performed.
Description
Citation
VELIČ, A. Optical study of laser-induced magnetic phase transitions [online]. Brno: Vysoké učení technické v Brně. Fakulta strojního inženýrství. 2022.
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Document version
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Language of document
en
Study field
bez specializace
Comittee
prof. RNDr. Tomáš Šikola, CSc. (předseda)
prof. RNDr. Jiří Spousta, Ph.D. (místopředseda)
doc. Ing. Stanislav Průša, Ph.D. (člen)
doc. Mgr. Vlastimil Křápek, Ph.D. (člen)
doc. Ing. Miroslav Bartošík, Ph.D. (člen)
prof. RNDr. Petr Dub, CSc. (člen)
prof. RNDr. Bohumila Lencová, CSc. (člen)
prof. RNDr. Miroslav Liška, DrSc. (člen)
doc. Ing. Miroslav Kolíbal, Ph.D. (člen)
prof. RNDr. Radim Chmelík, Ph.D. (člen)
doc. Ing. Radek Kalousek, Ph.D. (člen)
RNDr. Antonín Fejfar, CSc. (člen)
Date of acceptance
2022-06-15
Defence
Po otázkách oponenta bylo diskutováno
Důvod nižší odrazivosti antiferomagnetické fáze.
Student na otázku odpověděl.
Result of defence
práce byla úspěšně obhájena
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Standardní licenční smlouva - přístup k plnému textu bez omezení